From 0412969c20dae43b127b5d813e7cef70feb9d132 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Juan=20Carlos=20Alfaro=20Jim=C3=A9nez?=
 <JuanCarlos.Alfaro@uclm.es>
Date: Wed, 1 Jul 2020 19:04:40 +0200
Subject: [PATCH 01/42] MNT Deprecate _estimator_type and replace by
 estimator_tags

---
 sklearn/base.py                              | 57 ++++++++++++++++----
 sklearn/feature_selection/_rfe.py            |  6 ++-
 sklearn/feature_selection/tests/test_rfe.py  | 11 +++-
 sklearn/model_selection/_search.py           |  8 +++
 sklearn/model_selection/tests/test_search.py |  9 ++++
 sklearn/pipeline.py                          |  9 ++++
 sklearn/tests/test_base.py                   | 17 ++++++
 sklearn/tests/test_pipeline.py               |  8 +++
 8 files changed, 113 insertions(+), 12 deletions(-)

diff --git a/sklearn/base.py b/sklearn/base.py
index 46398baabfd3a..f6dcde5c1a1c2 100644
--- a/sklearn/base.py
+++ b/sklearn/base.py
@@ -19,6 +19,7 @@
 from .utils.validation import check_array
 from .utils._estimator_html_repr import estimator_html_repr
 from .utils.validation import _deprecate_positional_args
+from .utils.deprecation import deprecated
 
 _DEFAULT_TAGS = {
     'non_deterministic': False,
@@ -37,6 +38,7 @@
     'binary_only': False,
     'requires_fit': True,
     'requires_y': False,
+    'estimator_type': None
     }
 
 
@@ -465,7 +467,12 @@ def _repr_mimebundle_(self, **kwargs):
 class ClassifierMixin:
     """Mixin class for all classifiers in scikit-learn."""
 
-    _estimator_type = "classifier"
+    # mypy error: Decorated property not supported
+    @deprecated("_estimator_type is deprecated in "
+                "0.24 and will be removed in 0.26")
+    @property
+    def _estimator_type(self):
+        return "classifier"
 
     def score(self, X, y, sample_weight=None):
         """
@@ -495,12 +502,18 @@ def score(self, X, y, sample_weight=None):
         return accuracy_score(y, self.predict(X), sample_weight=sample_weight)
 
     def _more_tags(self):
-        return {'requires_y': True}
+        return {'requires_y': True, 'estimator_type': 'classifier'}
 
 
 class RegressorMixin:
     """Mixin class for all regression estimators in scikit-learn."""
-    _estimator_type = "regressor"
+
+    # mypy error: Decorated property not supported
+    @deprecated("_estimator_type is deprecated in "
+                "0.24 and will be removed in 0.26")
+    @property
+    def _estimator_type(self):
+        return "regressor"
 
     def score(self, X, y, sample_weight=None):
         """Return the coefficient of determination R^2 of the prediction.
@@ -548,12 +561,18 @@ def score(self, X, y, sample_weight=None):
         return r2_score(y, y_pred, sample_weight=sample_weight)
 
     def _more_tags(self):
-        return {'requires_y': True}
+        return {'requires_y': True, 'estimator_type': 'regressor'}
 
 
 class ClusterMixin:
     """Mixin class for all cluster estimators in scikit-learn."""
-    _estimator_type = "clusterer"
+
+    # mypy error: Decorated property not supported
+    @deprecated("_estimator_type is deprecated in "
+                "0.24 and will be removed in 0.26")
+    @property
+    def _estimator_type(self):
+        return "clusterer"
 
     def fit_predict(self, X, y=None):
         """
@@ -692,7 +711,13 @@ def fit_transform(self, X, y=None, **fit_params):
 
 class DensityMixin:
     """Mixin class for all density estimators in scikit-learn."""
-    _estimator_type = "DensityEstimator"
+
+    # mypy error: Decorated property not supported
+    @deprecated("_estimator_type is deprecated in "
+                "0.24 and will be removed in 0.26")
+    @property
+    def _estimator_type(self):
+        return "DensityEstimator"
 
     def score(self, X, y=None):
         """Return the score of the model on the data X
@@ -710,10 +735,19 @@ def score(self, X, y=None):
         """
         pass
 
+    def _more_tags(self):
+        return {'estimator_type': 'DensityEstimator'}
+
 
 class OutlierMixin:
     """Mixin class for all outlier detection estimators in scikit-learn."""
-    _estimator_type = "outlier_detector"
+
+    # mypy error: Decorated property not supported
+    @deprecated("_estimator_type is deprecated in "
+                "0.24 and will be removed in 0.26")
+    @property
+    def _estimator_type(self):
+        return "outlier_detector"
 
     def fit_predict(self, X, y=None):
         """Perform fit on X and returns labels for X.
@@ -736,6 +770,9 @@ def fit_predict(self, X, y=None):
         # override for transductive outlier detectors like LocalOulierFactor
         return self.fit(X).predict(X)
 
+    def _more_tags(self):
+        return {'estimator_type': 'outlier_detector'}
+
 
 class MetaEstimatorMixin:
     _required_parameters = ["estimator"]
@@ -768,7 +805,7 @@ def is_classifier(estimator):
     out : bool
         True if estimator is a classifier and False otherwise.
     """
-    return getattr(estimator, "_estimator_type", None) == "classifier"
+    return estimator._get_tags()["estimator_type"] == "classifier"
 
 
 def is_regressor(estimator):
@@ -784,7 +821,7 @@ def is_regressor(estimator):
     out : bool
         True if estimator is a regressor and False otherwise.
     """
-    return getattr(estimator, "_estimator_type", None) == "regressor"
+    return estimator._get_tags()["estimator_type"] == "regressor"
 
 
 def is_outlier_detector(estimator):
@@ -800,4 +837,4 @@ def is_outlier_detector(estimator):
     out : bool
         True if estimator is an outlier detector and False otherwise.
     """
-    return getattr(estimator, "_estimator_type", None) == "outlier_detector"
+    return estimator._get_tags()["estimator_type"] == "outlier_detector"
diff --git a/sklearn/feature_selection/_rfe.py b/sklearn/feature_selection/_rfe.py
index 5e0e8ffc6f6d8..af6e4d0ffcd39 100644
--- a/sklearn/feature_selection/_rfe.py
+++ b/sklearn/feature_selection/_rfe.py
@@ -14,6 +14,7 @@
 from ..utils.metaestimators import _safe_split
 from ..utils.validation import check_is_fitted
 from ..utils.validation import _deprecate_positional_args
+from ..utils.deprecation import deprecated
 from ..base import BaseEstimator
 from ..base import MetaEstimatorMixin
 from ..base import clone
@@ -149,6 +150,9 @@ def __init__(self, estimator, *, n_features_to_select=None, step=1,
         self.importance_getter = importance_getter
         self.verbose = verbose
 
+    # mypy error: Decorated property not supported
+    @deprecated("_estimator_type is deprecated in "
+                "0.24 and will be removed in 0.26")
     @property
     def _estimator_type(self):
         return self.estimator._estimator_type
@@ -365,7 +369,7 @@ def _more_tags(self):
         return {'poor_score': True,
                 'allow_nan': estimator_tags.get('allow_nan', True),
                 'requires_y': True,
-                }
+                'estimator_type': estimator_tags['estimator_type']}
 
 
 class RFECV(RFE):
diff --git a/sklearn/feature_selection/tests/test_rfe.py b/sklearn/feature_selection/tests/test_rfe.py
index adb371f5fc006..1b19ff677397e 100644
--- a/sklearn/feature_selection/tests/test_rfe.py
+++ b/sklearn/feature_selection/tests/test_rfe.py
@@ -57,7 +57,7 @@ def set_params(self, **params):
         return self
 
     def _get_tags(self):
-        return {}
+        return {'estimator_type': 'classifier'}
 
 
 def test_rfe_features_importance():
@@ -280,6 +280,7 @@ def test_rfecv_grid_scores_size():
         assert rfecv.n_features_ >= min_features_to_select
 
 
+@ignore_warnings(category=FutureWarning)
 def test_rfe_estimator_tags():
     rfe = RFE(SVC(kernel='linear'))
     assert rfe._estimator_type == "classifier"
@@ -491,3 +492,11 @@ def test_multioutput(ClsRFE):
     clf = RandomForestClassifier(n_estimators=5)
     rfe_test = ClsRFE(clf)
     rfe_test.fit(X, y)
+
+
+# TODO: Remove in version 0.26
+def test_deprecated_estimator_type():
+    # Assert that deprecated _estimator_type warns FutureWarning
+    rfe = RFE(SVC())
+    with pytest.warns(FutureWarning):
+        hasattr(rfe, "_estimator_type")
diff --git a/sklearn/model_selection/_search.py b/sklearn/model_selection/_search.py
index bcdbcdbc498fb..6007408c6631b 100644
--- a/sklearn/model_selection/_search.py
+++ b/sklearn/model_selection/_search.py
@@ -419,6 +419,8 @@ def __init__(self, estimator, *, scoring=None, n_jobs=None,
         self.return_train_score = return_train_score
 
     @property
+    @deprecated("_estimator_type is deprecated in "
+                "0.24 and will be removed in 0.26")
     def _estimator_type(self):
         return self.estimator._estimator_type
 
@@ -867,6 +869,12 @@ def _store(key_name, array, weights=None, splits=False, rank=False):
 
         return results
 
+    def _more_tags(self):
+        estimator_tags = self.estimator._get_tags()
+        return {
+            'estimator_type': estimator_tags['estimator_type']
+        }
+
 
 class GridSearchCV(BaseSearchCV):
     """Exhaustive search over specified parameter values for an estimator.
diff --git a/sklearn/model_selection/tests/test_search.py b/sklearn/model_selection/tests/test_search.py
index cd01916d28ea9..337837849a160 100644
--- a/sklearn/model_selection/tests/test_search.py
+++ b/sklearn/model_selection/tests/test_search.py
@@ -1885,3 +1885,12 @@ def _fit_param_callable():
         'scalar_param': 42,
     }
     model.fit(X_train, y_train, **fit_params)
+
+
+# TODO: Remove in version 0.26
+@pytest.mark.parametrize("SearchCV", [GridSearchCV, RandomizedSearchCV])
+def test_deprecated_estimator_type(SearchCV):
+    # Assert that deprecated _estimator_type warns FutureWarning
+    search = SearchCV(DecisionTreeClassifier(), {'max_depth': [5, 10]})
+    with pytest.warns(FutureWarning):
+        hasattr(search, "_estimator_type")
diff --git a/sklearn/pipeline.py b/sklearn/pipeline.py
index cd85f664afde4..1ea54870b14f4 100644
--- a/sklearn/pipeline.py
+++ b/sklearn/pipeline.py
@@ -22,6 +22,7 @@
 from .utils import Bunch, _print_elapsed_time
 from .utils.validation import check_memory
 from .utils.validation import _deprecate_positional_args
+from .utils.deprecation import deprecated
 
 from .utils.metaestimators import _BaseComposition
 
@@ -212,6 +213,8 @@ def __getitem__(self, ind):
         return est
 
     @property
+    @deprecated("_estimator_type is deprecated in "
+                "0.24 and will be removed in 0.26")
     def _estimator_type(self):
         return self.steps[-1][1]._estimator_type
 
@@ -638,6 +641,12 @@ def _get_name(name, est):
                             name_details=name_details,
                             dash_wrapped=False)
 
+    def _more_tags(self):
+        estimator_tags = self.steps[-1][1]._get_tags()
+        return {
+            'estimator_type': estimator_tags['estimator_type']
+        }
+
 
 def _name_estimators(estimators):
     """Generate names for estimators."""
diff --git a/sklearn/tests/test_base.py b/sklearn/tests/test_base.py
index db5c88051346a..fe006aa66a33a 100644
--- a/sklearn/tests/test_base.py
+++ b/sklearn/tests/test_base.py
@@ -21,6 +21,10 @@
 from sklearn.tree import DecisionTreeRegressor
 from sklearn import datasets
 
+from sklearn.cluster import KMeans
+from sklearn.mixture import BayesianGaussianMixture
+from sklearn.ensemble import IsolationForest
+
 from sklearn.base import TransformerMixin
 from sklearn.utils._mocking import MockDataFrame
 from sklearn import config_context
@@ -537,3 +541,16 @@ def test_repr_html_wraps():
     with config_context(display='diagram'):
         output = tree._repr_html_()
         assert "<style>" in output
+
+
+# TODO: Remove in version 0.26
+@pytest.mark.parametrize("Estimator", [DecisionTreeClassifier,
+                                       DecisionTreeRegressor,
+                                       KMeans,
+                                       BayesianGaussianMixture,
+                                       IsolationForest])
+def test_deprecated_estimator_type(Estimator):
+    # Assert that deprecated _estimator_type warns FutureWarning
+    est = Estimator()
+    with pytest.warns(FutureWarning):
+        hasattr(est, "_estimator_type")
diff --git a/sklearn/tests/test_pipeline.py b/sklearn/tests/test_pipeline.py
index 3f838d044a1e1..a763e8f94be78 100644
--- a/sklearn/tests/test_pipeline.py
+++ b/sklearn/tests/test_pipeline.py
@@ -1220,3 +1220,11 @@ def transform(self, X, y=None):
 
     t.fit(X, y, a=0)
     t.fit_transform(X, y, a=0)
+
+
+# TODO: Remove in version 0.26
+def test_deprecated_estimator_type():
+    # Assert that deprecated _estimator_type warns FutureWarning
+    pipeline = Pipeline([('est', LinearRegression())])
+    with pytest.warns(FutureWarning):
+        hasattr(pipeline, "_estimator_type")

From 2aead16422d459e46b33c59a323db8c5c91b09e7 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Juan=20Carlos=20Alfaro=20Jim=C3=A9nez?=
 <JuanCarlos.Alfaro@uclm.es>
Date: Wed, 1 Jul 2020 19:11:15 +0200
Subject: [PATCH 02/42] MNT Replace _estimator_type attribute in glossary by
 estimator_type tag

---
 doc/glossary.rst | 11 ++---------
 1 file changed, 2 insertions(+), 9 deletions(-)

diff --git a/doc/glossary.rst b/doc/glossary.rst
index 86cb3c06f5634..9210a9baf9333 100644
--- a/doc/glossary.rst
+++ b/doc/glossary.rst
@@ -356,13 +356,6 @@ General Concepts
 
         .. glossary::
 
-            ``_estimator_type``
-                This string-valued attribute identifies an estimator as being a
-                classifier, regressor, etc. It is set by mixins such as
-                :class:`base.ClassifierMixin`, but needs to be more explicitly
-                adopted on a :term:`meta-estimator`.  Its value should usually be
-                checked by way of a helper such as :func:`base.is_classifier`.
-
             ``_pairwise``
                 This boolean attribute indicates whether the data (``X``) passed to
                 :func:`fit` and similar methods consists of pairwise measures over
@@ -798,7 +791,7 @@ Class APIs and Estimator Types
 
         Classifiers must store a :term:`classes_` attribute after fitting,
         and usually inherit from :class:`base.ClassifierMixin`, which sets
-        their :term:`_estimator_type` attribute.
+        their estimator_type tag.
 
         A classifier can be distinguished from other estimators with
         :func:`~base.is_classifier`.
@@ -936,7 +929,7 @@ Class APIs and Estimator Types
         with :term:`continuous` output values.
 
         Regressors usually inherit from :class:`base.RegressorMixin`, which
-        sets their :term:`_estimator_type` attribute.
+        sets their `estimator_type` tag.
 
         A regressor can be distinguished from other estimators with
         :func:`~base.is_regressor`.

From a907782c17a217e9a3d13a5e97137c52ed2aeba9 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Juan=20Carlos=20Alfaro=20Jim=C3=A9nez?=
 <JuanCarlos.Alfaro@uclm.es>
Date: Wed, 1 Jul 2020 19:13:04 +0200
Subject: [PATCH 03/42] MNT Replace _estimator_type attribute in develop by
 estimator_type tag

---
 doc/developers/develop.rst | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/doc/developers/develop.rst b/doc/developers/develop.rst
index 53dd0ca47824d..c03328f536efa 100644
--- a/doc/developers/develop.rst
+++ b/doc/developers/develop.rst
@@ -410,12 +410,12 @@ For example, cross-validation in :class:`model_selection.GridSearchCV` and
 on a classifier, but not otherwise. Similarly, scorers for average precision
 that take a continuous prediction need to call ``decision_function`` for classifiers,
 but ``predict`` for regressors. This distinction between classifiers and regressors
-is implemented using the ``_estimator_type`` attribute, which takes a string value.
+is implemented using the ``estimator_type`` tag, which takes a string value.
 It should be ``"classifier"`` for classifiers and ``"regressor"`` for
 regressors and ``"clusterer"`` for clustering methods, to work as expected.
 Inheriting from ``ClassifierMixin``, ``RegressorMixin`` or ``ClusterMixin``
 will set the attribute automatically.  When a meta-estimator needs to distinguish
-among estimator types, instead of checking ``_estimator_type`` directly, helpers
+among estimator types, instead of checking ``estimator_type`` tag, helpers
 like :func:`base.is_classifier` should be used.
 
 Specific models

From d501d1c17b21cb9cec1274e9f5910133db992196 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Juan=20Carlos=20Alfaro=20Jim=C3=A9nez?=
 <JuanCarlos.Alfaro@uclm.es>
Date: Wed, 1 Jul 2020 19:14:52 +0200
Subject: [PATCH 04/42] FIX Fix lint

---
 sklearn/model_selection/_search.py | 3 ++-
 sklearn/pipeline.py                | 3 ++-
 2 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/sklearn/model_selection/_search.py b/sklearn/model_selection/_search.py
index 6007408c6631b..fb83dda5c6f4d 100644
--- a/sklearn/model_selection/_search.py
+++ b/sklearn/model_selection/_search.py
@@ -418,9 +418,10 @@ def __init__(self, estimator, *, scoring=None, n_jobs=None,
         self.error_score = error_score
         self.return_train_score = return_train_score
 
-    @property
+    # mypy error: Decorated property not supported
     @deprecated("_estimator_type is deprecated in "
                 "0.24 and will be removed in 0.26")
+    @property
     def _estimator_type(self):
         return self.estimator._estimator_type
 
diff --git a/sklearn/pipeline.py b/sklearn/pipeline.py
index 1ea54870b14f4..26268fcfdf86a 100644
--- a/sklearn/pipeline.py
+++ b/sklearn/pipeline.py
@@ -212,9 +212,10 @@ def __getitem__(self, ind):
             return self.named_steps[ind]
         return est
 
-    @property
+    # mypy error: Decorated property not supported
     @deprecated("_estimator_type is deprecated in "
                 "0.24 and will be removed in 0.26")
+    @property
     def _estimator_type(self):
         return self.steps[-1][1]._estimator_type
 

From f91c369f507764609418f1c998cb9ec4e0277472 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Juan=20Carlos=20Alfaro=20Jim=C3=A9nez?=
 <JuanCarlos.Alfaro@uclm.es>
Date: Wed, 1 Jul 2020 19:19:11 +0200
Subject: [PATCH 05/42] FIX Fix lint

---
 sklearn/base.py                    | 10 +++++-----
 sklearn/feature_selection/_rfe.py  |  2 +-
 sklearn/model_selection/_search.py |  2 +-
 sklearn/pipeline.py                |  2 +-
 4 files changed, 8 insertions(+), 8 deletions(-)

diff --git a/sklearn/base.py b/sklearn/base.py
index f6dcde5c1a1c2..386d44ccc00a4 100644
--- a/sklearn/base.py
+++ b/sklearn/base.py
@@ -468,7 +468,7 @@ class ClassifierMixin:
     """Mixin class for all classifiers in scikit-learn."""
 
     # mypy error: Decorated property not supported
-    @deprecated("_estimator_type is deprecated in "
+    @deprecated("_estimator_type is deprecated in "  # type: ignore
                 "0.24 and will be removed in 0.26")
     @property
     def _estimator_type(self):
@@ -509,7 +509,7 @@ class RegressorMixin:
     """Mixin class for all regression estimators in scikit-learn."""
 
     # mypy error: Decorated property not supported
-    @deprecated("_estimator_type is deprecated in "
+    @deprecated("_estimator_type is deprecated in "  # type: ignore
                 "0.24 and will be removed in 0.26")
     @property
     def _estimator_type(self):
@@ -568,7 +568,7 @@ class ClusterMixin:
     """Mixin class for all cluster estimators in scikit-learn."""
 
     # mypy error: Decorated property not supported
-    @deprecated("_estimator_type is deprecated in "
+    @deprecated("_estimator_type is deprecated in "  # type: ignore
                 "0.24 and will be removed in 0.26")
     @property
     def _estimator_type(self):
@@ -713,7 +713,7 @@ class DensityMixin:
     """Mixin class for all density estimators in scikit-learn."""
 
     # mypy error: Decorated property not supported
-    @deprecated("_estimator_type is deprecated in "
+    @deprecated("_estimator_type is deprecated in "  # type: ignore
                 "0.24 and will be removed in 0.26")
     @property
     def _estimator_type(self):
@@ -743,7 +743,7 @@ class OutlierMixin:
     """Mixin class for all outlier detection estimators in scikit-learn."""
 
     # mypy error: Decorated property not supported
-    @deprecated("_estimator_type is deprecated in "
+    @deprecated("_estimator_type is deprecated in "  # type: ignore
                 "0.24 and will be removed in 0.26")
     @property
     def _estimator_type(self):
diff --git a/sklearn/feature_selection/_rfe.py b/sklearn/feature_selection/_rfe.py
index af6e4d0ffcd39..5e1eefe62cf26 100644
--- a/sklearn/feature_selection/_rfe.py
+++ b/sklearn/feature_selection/_rfe.py
@@ -151,7 +151,7 @@ def __init__(self, estimator, *, n_features_to_select=None, step=1,
         self.verbose = verbose
 
     # mypy error: Decorated property not supported
-    @deprecated("_estimator_type is deprecated in "
+    @deprecated("_estimator_type is deprecated in "  # type: ignore
                 "0.24 and will be removed in 0.26")
     @property
     def _estimator_type(self):
diff --git a/sklearn/model_selection/_search.py b/sklearn/model_selection/_search.py
index fb83dda5c6f4d..555cc464add6b 100644
--- a/sklearn/model_selection/_search.py
+++ b/sklearn/model_selection/_search.py
@@ -419,7 +419,7 @@ def __init__(self, estimator, *, scoring=None, n_jobs=None,
         self.return_train_score = return_train_score
 
     # mypy error: Decorated property not supported
-    @deprecated("_estimator_type is deprecated in "
+    @deprecated("_estimator_type is deprecated in "  # type: ignore
                 "0.24 and will be removed in 0.26")
     @property
     def _estimator_type(self):
diff --git a/sklearn/pipeline.py b/sklearn/pipeline.py
index 26268fcfdf86a..d42d536376193 100644
--- a/sklearn/pipeline.py
+++ b/sklearn/pipeline.py
@@ -213,7 +213,7 @@ def __getitem__(self, ind):
         return est
 
     # mypy error: Decorated property not supported
-    @deprecated("_estimator_type is deprecated in "
+    @deprecated("_estimator_type is deprecated in "  # type: ignore
                 "0.24 and will be removed in 0.26")
     @property
     def _estimator_type(self):

From 17f581e41f4d438f98209a4b3f3edd5dce2e7991 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Juan=20Carlos=20Alfaro=20Jim=C3=A9nez?=
 <JuanCarlos.Alfaro@uclm.es>
Date: Wed, 1 Jul 2020 19:20:22 +0200
Subject: [PATCH 06/42] MNT Minor change

---
 doc/glossary.rst | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/doc/glossary.rst b/doc/glossary.rst
index 9210a9baf9333..af7d87d9238fc 100644
--- a/doc/glossary.rst
+++ b/doc/glossary.rst
@@ -791,7 +791,7 @@ Class APIs and Estimator Types
 
         Classifiers must store a :term:`classes_` attribute after fitting,
         and usually inherit from :class:`base.ClassifierMixin`, which sets
-        their estimator_type tag.
+        their `estimator_type` tag.
 
         A classifier can be distinguished from other estimators with
         :func:`~base.is_classifier`.

From 376231f1e8b3e69c590f8d971d8d200502a924db Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Juan=20Carlos=20Alfaro=20Jim=C3=A9nez?=
 <JuanCarlos.Alfaro@uclm.es>
Date: Fri, 3 Jul 2020 15:08:32 +0200
Subject: [PATCH 07/42] FIX Remove estimator_type from DEFAULT_TAGS

---
 sklearn/base.py | 15 ++++++++++-----
 1 file changed, 10 insertions(+), 5 deletions(-)

diff --git a/sklearn/base.py b/sklearn/base.py
index 386d44ccc00a4..54337a5493aab 100644
--- a/sklearn/base.py
+++ b/sklearn/base.py
@@ -37,8 +37,7 @@
     'multioutput_only': False,
     'binary_only': False,
     'requires_fit': True,
-    'requires_y': False,
-    'estimator_type': None
+    'requires_y': False
     }
 
 
@@ -805,7 +804,9 @@ def is_classifier(estimator):
     out : bool
         True if estimator is a classifier and False otherwise.
     """
-    return estimator._get_tags()["estimator_type"] == "classifier"
+    estimator_tags = estimator._get_tags()
+    return ("estimator_type" in estimator_tags and
+            estimator_tags["estimator_type"] == "classifier")
 
 
 def is_regressor(estimator):
@@ -821,7 +822,9 @@ def is_regressor(estimator):
     out : bool
         True if estimator is a regressor and False otherwise.
     """
-    return estimator._get_tags()["estimator_type"] == "regressor"
+    estimator_tags = estimator._get_tags()
+    return ("estimator_type" in estimator_tags and
+            estimator_tags["estimator_type"] == "regressor")
 
 
 def is_outlier_detector(estimator):
@@ -837,4 +840,6 @@ def is_outlier_detector(estimator):
     out : bool
         True if estimator is an outlier detector and False otherwise.
     """
-    return estimator._get_tags()["estimator_type"] == "outlier_detector"
+    estimator_tags = estimator._get_tags()
+    return ("estimator_type" in estimator_tags and
+            estimator_tags["estimator_type"] == "outlier_detector")

From 99766bbbc2cc242480a27639d064a5b065db5adf Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Juan=20Carlos=20Alfaro=20Jim=C3=A9nez?=
 <JuanCarlos.Alfaro@uclm.es>
Date: Fri, 3 Jul 2020 15:44:49 +0200
Subject: [PATCH 08/42] MNT Use simpler solution

---
 sklearn/base.py | 11 +++--------
 1 file changed, 3 insertions(+), 8 deletions(-)

diff --git a/sklearn/base.py b/sklearn/base.py
index 54337a5493aab..98f7ac7cb2b7c 100644
--- a/sklearn/base.py
+++ b/sklearn/base.py
@@ -804,9 +804,7 @@ def is_classifier(estimator):
     out : bool
         True if estimator is a classifier and False otherwise.
     """
-    estimator_tags = estimator._get_tags()
-    return ("estimator_type" in estimator_tags and
-            estimator_tags["estimator_type"] == "classifier")
+    return estimator._get_tags().get("estimator_type", None) == "classifier"
 
 
 def is_regressor(estimator):
@@ -822,9 +820,7 @@ def is_regressor(estimator):
     out : bool
         True if estimator is a regressor and False otherwise.
     """
-    estimator_tags = estimator._get_tags()
-    return ("estimator_type" in estimator_tags and
-            estimator_tags["estimator_type"] == "regressor")
+    return estimator._get_tags().get("estimator_type", None) == "regressor"
 
 
 def is_outlier_detector(estimator):
@@ -841,5 +837,4 @@ def is_outlier_detector(estimator):
         True if estimator is an outlier detector and False otherwise.
     """
     estimator_tags = estimator._get_tags()
-    return ("estimator_type" in estimator_tags and
-            estimator_tags["estimator_type"] == "outlier_detector")
+    return estimator_tags.get("estimator_type", None) == "outlier_detector"

From 8158a5f20e9b2387bf415f99a24e92ca498ba57e Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Juan=20Carlos=20Alfaro=20Jim=C3=A9nez?=
 <JuanCarlos.Alfaro@uclm.es>
Date: Fri, 3 Jul 2020 16:00:37 +0200
Subject: [PATCH 09/42] FIX Check if estimator has estimator_type attribute

---
 sklearn/base.py | 16 ++++++++++++----
 1 file changed, 12 insertions(+), 4 deletions(-)

diff --git a/sklearn/base.py b/sklearn/base.py
index 98f7ac7cb2b7c..9af927a6f1288 100644
--- a/sklearn/base.py
+++ b/sklearn/base.py
@@ -804,7 +804,10 @@ def is_classifier(estimator):
     out : bool
         True if estimator is a classifier and False otherwise.
     """
-    return estimator._get_tags().get("estimator_type", None) == "classifier"
+    return (
+        hasattr(estimator, "_get_tags") and
+        estimator._get_tags().get("estimator_type", None) == "classifier"
+    )
 
 
 def is_regressor(estimator):
@@ -820,7 +823,10 @@ def is_regressor(estimator):
     out : bool
         True if estimator is a regressor and False otherwise.
     """
-    return estimator._get_tags().get("estimator_type", None) == "regressor"
+    return (
+        hasattr(estimator, "_get_tags") and
+        estimator._get_tags().get("estimator_type", None) == "regressor"
+    )
 
 
 def is_outlier_detector(estimator):
@@ -836,5 +842,7 @@ def is_outlier_detector(estimator):
     out : bool
         True if estimator is an outlier detector and False otherwise.
     """
-    estimator_tags = estimator._get_tags()
-    return estimator_tags.get("estimator_type", None) == "outlier_detector"
+    return (
+        hasattr(estimator, "_get_tags") and
+        estimator._get_tags().get("estimator_type", None) == "outlier_detector"
+    )

From 24c6fe4315754de483663735b92c93db195820db Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Juan=20Carlos=20Alfaro=20Jim=C3=A9nez?=
 <JuanCarlos.Alfaro@uclm.es>
Date: Fri, 3 Jul 2020 16:39:06 +0200
Subject: [PATCH 10/42] MNT Use getattr to return a dict if _get_tags is not
 defined

---
 sklearn/base.py | 18 ++++++------------
 1 file changed, 6 insertions(+), 12 deletions(-)

diff --git a/sklearn/base.py b/sklearn/base.py
index 9af927a6f1288..3600aa7960def 100644
--- a/sklearn/base.py
+++ b/sklearn/base.py
@@ -804,10 +804,8 @@ def is_classifier(estimator):
     out : bool
         True if estimator is a classifier and False otherwise.
     """
-    return (
-        hasattr(estimator, "_get_tags") and
-        estimator._get_tags().get("estimator_type", None) == "classifier"
-    )
+    estimator_tags = getattr(estimator, "_get_tags", dict)()
+    return estimator_tags.get("estimator_type", None) == "classifier"
 
 
 def is_regressor(estimator):
@@ -823,10 +821,8 @@ def is_regressor(estimator):
     out : bool
         True if estimator is a regressor and False otherwise.
     """
-    return (
-        hasattr(estimator, "_get_tags") and
-        estimator._get_tags().get("estimator_type", None) == "regressor"
-    )
+    estimator_tags = getattr(estimator, "_get_tags", dict)()
+    return estimator_tags.get("estimator_type", None) == "regressor"
 
 
 def is_outlier_detector(estimator):
@@ -842,7 +838,5 @@ def is_outlier_detector(estimator):
     out : bool
         True if estimator is an outlier detector and False otherwise.
     """
-    return (
-        hasattr(estimator, "_get_tags") and
-        estimator._get_tags().get("estimator_type", None) == "outlier_detector"
-    )
+    estimator_tags = getattr(estimator, "_get_tags", dict)()
+    return estimator_tags.get("estimator_type", None) == "outlier_detector"

From 2b732e56ec4bdb858adfeb4c48d2c546c8436e01 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Juan=20Carlos=20Alfaro=20Jim=C3=A9nez?=
 <JuanCarlos.Alfaro@uclm.es>
Date: Fri, 3 Jul 2020 17:02:21 +0200
Subject: [PATCH 11/42] FIX Minor changes

---
 sklearn/feature_selection/_rfe.py  | 2 +-
 sklearn/model_selection/_search.py | 5 +----
 sklearn/pipeline.py                | 5 +----
 3 files changed, 3 insertions(+), 9 deletions(-)

diff --git a/sklearn/feature_selection/_rfe.py b/sklearn/feature_selection/_rfe.py
index 5e1eefe62cf26..3615f19e4a94f 100644
--- a/sklearn/feature_selection/_rfe.py
+++ b/sklearn/feature_selection/_rfe.py
@@ -369,7 +369,7 @@ def _more_tags(self):
         return {'poor_score': True,
                 'allow_nan': estimator_tags.get('allow_nan', True),
                 'requires_y': True,
-                'estimator_type': estimator_tags['estimator_type']}
+                'estimator_type': estimator_tags.get('estimator_type', None)}
 
 
 class RFECV(RFE):
diff --git a/sklearn/model_selection/_search.py b/sklearn/model_selection/_search.py
index 555cc464add6b..be087d0679dd5 100644
--- a/sklearn/model_selection/_search.py
+++ b/sklearn/model_selection/_search.py
@@ -871,10 +871,7 @@ def _store(key_name, array, weights=None, splits=False, rank=False):
         return results
 
     def _more_tags(self):
-        estimator_tags = self.estimator._get_tags()
-        return {
-            'estimator_type': estimator_tags['estimator_type']
-        }
+        return getattr(self.estimator, "_get_tags", dict)()
 
 
 class GridSearchCV(BaseSearchCV):
diff --git a/sklearn/pipeline.py b/sklearn/pipeline.py
index d42d536376193..6b595064b9949 100644
--- a/sklearn/pipeline.py
+++ b/sklearn/pipeline.py
@@ -643,10 +643,7 @@ def _get_name(name, est):
                             dash_wrapped=False)
 
     def _more_tags(self):
-        estimator_tags = self.steps[-1][1]._get_tags()
-        return {
-            'estimator_type': estimator_tags['estimator_type']
-        }
+        return getattr(self.steps[-1][1], "_get_tags", dict)()
 
 
 def _name_estimators(estimators):

From 9d55a165885a6ab8cb4e13d4d694ce0520ca4d0e Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Juan=20Carlos=20Alfaro=20Jim=C3=A9nez?=
 <JuanCarlos.Alfaro@uclm.es>
Date: Fri, 3 Jul 2020 17:46:16 +0200
Subject: [PATCH 12/42] FIX Fix changes to make the CI to pass

---
 sklearn/metrics/_plot/tests/test_plot_roc_curve.py | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/sklearn/metrics/_plot/tests/test_plot_roc_curve.py b/sklearn/metrics/_plot/tests/test_plot_roc_curve.py
index 50e69ad41af8d..ff77f7eb7a398 100644
--- a/sklearn/metrics/_plot/tests/test_plot_roc_curve.py
+++ b/sklearn/metrics/_plot/tests/test_plot_roc_curve.py
@@ -8,6 +8,7 @@
 from sklearn.datasets import load_iris
 from sklearn.linear_model import LogisticRegression
 from sklearn.metrics import roc_curve, auc
+from sklearn.base import BaseEstimator
 from sklearn.base import ClassifierMixin
 from sklearn.exceptions import NotFittedError
 from sklearn.pipeline import make_pipeline
@@ -56,7 +57,7 @@ def test_plot_roc_curve_error_no_response(pyplot, data_binary, response_method,
                                           msg):
     X, y = data_binary
 
-    class MyClassifier(ClassifierMixin):
+    class MyClassifier(BaseEstimator, ClassifierMixin):
         def fit(self, X, y):
             self.classes_ = [0, 1]
             return self

From 05fe2035d0cad1f4898e6c572345d162d8c769c7 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Juan=20Carlos=20Alfaro=20Jim=C3=A9nez?=
 <JuanCarlos.Alfaro@uclm.es>
Date: Fri, 3 Jul 2020 17:51:16 +0200
Subject: [PATCH 13/42] DOC Add meaning of estimator_type to developing
 estimators

---
 doc/developers/develop.rst | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/doc/developers/develop.rst b/doc/developers/develop.rst
index c03328f536efa..9f8312f8b0e00 100644
--- a/doc/developers/develop.rst
+++ b/doc/developers/develop.rst
@@ -479,6 +479,12 @@ binary_only (default=False)
     whether estimator supports binary classification but lacks multi-class
     classification support.
 
+estimator_type (default=None)
+    string-valued identifier of an estimator as being a classifier, regressor,
+    etc. It is set by mixins such as :class:`~base.ClassifierMixin`, but needs
+    to be more explicitly adopted on a :term:`meta-estimator`. Its value should
+    usually be checked by way of a helper such as :func:`base.is_classifier`.
+
 multilabel (default=False)
     whether the estimator supports multilabel output
 

From 56cc0f09b957723280da5d4de55f19f2c7265486 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Juan=20Carlos=20Alfaro=20Jim=C3=A9nez?=
 <JuanCarlos.Alfaro@uclm.es>
Date: Fri, 3 Jul 2020 18:08:25 +0200
Subject: [PATCH 14/42] Trigger CI again


From 754066337b98907c56e85ccda8ea05f0fa8392f0 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Juan=20Carlos=20Alfaro=20Jim=C3=A9nez?=
 <JuanCarlos.Alfaro@uclm.es>
Date: Sun, 5 Jul 2020 18:53:35 +0200
Subject: [PATCH 15/42] CLN Apply suggested changes

---
 doc/glossary.rst                             |  4 ++--
 sklearn/base.py                              | 18 +++++++++++-------
 sklearn/feature_selection/tests/test_rfe.py  |  4 ++--
 sklearn/model_selection/_search.py           |  2 +-
 sklearn/model_selection/tests/test_search.py |  4 ++--
 sklearn/pipeline.py                          |  2 +-
 sklearn/tests/test_base.py                   | 16 ++++++++++++++--
 7 files changed, 33 insertions(+), 17 deletions(-)

diff --git a/doc/glossary.rst b/doc/glossary.rst
index af7d87d9238fc..00e529f3ee2cf 100644
--- a/doc/glossary.rst
+++ b/doc/glossary.rst
@@ -791,7 +791,7 @@ Class APIs and Estimator Types
 
         Classifiers must store a :term:`classes_` attribute after fitting,
         and usually inherit from :class:`base.ClassifierMixin`, which sets
-        their `estimator_type` tag.
+        their :ref:`estimator_type <estimator_tags>` tag.
 
         A classifier can be distinguished from other estimators with
         :func:`~base.is_classifier`.
@@ -929,7 +929,7 @@ Class APIs and Estimator Types
         with :term:`continuous` output values.
 
         Regressors usually inherit from :class:`base.RegressorMixin`, which
-        sets their `estimator_type` tag.
+        sets their :ref:`estimator_type <estimator_tags>` tag.
 
         A regressor can be distinguished from other estimators with
         :func:`~base.is_regressor`.
diff --git a/sklearn/base.py b/sklearn/base.py
index 3600aa7960def..f9c3ba960c1c9 100644
--- a/sklearn/base.py
+++ b/sklearn/base.py
@@ -37,7 +37,8 @@
     'multioutput_only': False,
     'binary_only': False,
     'requires_fit': True,
-    'requires_y': False
+    'requires_y': False,
+    'estimator_type': None
     }
 
 
@@ -595,6 +596,9 @@ def fit_predict(self, X, y=None):
         self.fit(X)
         return self.labels_
 
+    def _more_tags(self):
+        return {'estimator_type': 'clusterer'}
+
 
 class BiclusterMixin:
     """Mixin class for all bicluster estimators in scikit-learn"""
@@ -804,8 +808,8 @@ def is_classifier(estimator):
     out : bool
         True if estimator is a classifier and False otherwise.
     """
-    estimator_tags = getattr(estimator, "_get_tags", dict)()
-    return estimator_tags.get("estimator_type", None) == "classifier"
+    estimator_tags = estimator._get_tags()
+    return estimator_tags["estimator_type"] == "classifier"
 
 
 def is_regressor(estimator):
@@ -821,8 +825,8 @@ def is_regressor(estimator):
     out : bool
         True if estimator is a regressor and False otherwise.
     """
-    estimator_tags = getattr(estimator, "_get_tags", dict)()
-    return estimator_tags.get("estimator_type", None) == "regressor"
+    estimator_tags = estimator._get_tags()
+    return estimator_tags["estimator_type"] == "regressor"
 
 
 def is_outlier_detector(estimator):
@@ -838,5 +842,5 @@ def is_outlier_detector(estimator):
     out : bool
         True if estimator is an outlier detector and False otherwise.
     """
-    estimator_tags = getattr(estimator, "_get_tags", dict)()
-    return estimator_tags.get("estimator_type", None) == "outlier_detector"
+    estimator_tags = estimator._get_tags()
+    return estimator_tags["estimator_type"] == "outlier_detector"
diff --git a/sklearn/feature_selection/tests/test_rfe.py b/sklearn/feature_selection/tests/test_rfe.py
index 1b19ff677397e..87dd30e08761f 100644
--- a/sklearn/feature_selection/tests/test_rfe.py
+++ b/sklearn/feature_selection/tests/test_rfe.py
@@ -498,5 +498,5 @@ def test_multioutput(ClsRFE):
 def test_deprecated_estimator_type():
     # Assert that deprecated _estimator_type warns FutureWarning
     rfe = RFE(SVC())
-    with pytest.warns(FutureWarning):
-        hasattr(rfe, "_estimator_type")
+    with pytest.warns(FutureWarning, match="estimator_type is deprecated"):
+        getattr(rfe, "_estimator_type")
diff --git a/sklearn/model_selection/_search.py b/sklearn/model_selection/_search.py
index be087d0679dd5..78253b6edd3fd 100644
--- a/sklearn/model_selection/_search.py
+++ b/sklearn/model_selection/_search.py
@@ -871,7 +871,7 @@ def _store(key_name, array, weights=None, splits=False, rank=False):
         return results
 
     def _more_tags(self):
-        return getattr(self.estimator, "_get_tags", dict)()
+        return self.estimator._more_tags()
 
 
 class GridSearchCV(BaseSearchCV):
diff --git a/sklearn/model_selection/tests/test_search.py b/sklearn/model_selection/tests/test_search.py
index 337837849a160..b2d67ef023dc7 100644
--- a/sklearn/model_selection/tests/test_search.py
+++ b/sklearn/model_selection/tests/test_search.py
@@ -1892,5 +1892,5 @@ def _fit_param_callable():
 def test_deprecated_estimator_type(SearchCV):
     # Assert that deprecated _estimator_type warns FutureWarning
     search = SearchCV(DecisionTreeClassifier(), {'max_depth': [5, 10]})
-    with pytest.warns(FutureWarning):
-        hasattr(search, "_estimator_type")
+    with pytest.warns(FutureWarning, match="estimator_type is deprecated"):
+        getattr(search, "_estimator_type")
diff --git a/sklearn/pipeline.py b/sklearn/pipeline.py
index 6b595064b9949..7af361b09cb6f 100644
--- a/sklearn/pipeline.py
+++ b/sklearn/pipeline.py
@@ -643,7 +643,7 @@ def _get_name(name, est):
                             dash_wrapped=False)
 
     def _more_tags(self):
-        return getattr(self.steps[-1][1], "_get_tags", dict)()
+        return self.steps[-1][1]._more_tags()
 
 
 def _name_estimators(estimators):
diff --git a/sklearn/tests/test_base.py b/sklearn/tests/test_base.py
index fe006aa66a33a..491f3dd39bcc6 100644
--- a/sklearn/tests/test_base.py
+++ b/sklearn/tests/test_base.py
@@ -543,6 +543,18 @@ def test_repr_html_wraps():
         assert "<style>" in output
 
 
+@pytest.mark.parametrize("Estimator,estimator_type",
+                         [(DecisionTreeClassifier, "classifier"),
+                          (DecisionTreeRegressor, "regressor"),
+                          (KMeans, "clusterer"),
+                          (BayesianGaussianMixture, "DensityEstimator"),
+                          (IsolationForest, "outlier_detector")])
+def test_estimator_type_tag(Estimator, estimator_type):
+    # Assert that the estimator_type tag is properly set
+    est = Estimator()
+    assert est._get_tags()["estimator_type"] == estimator_type
+
+
 # TODO: Remove in version 0.26
 @pytest.mark.parametrize("Estimator", [DecisionTreeClassifier,
                                        DecisionTreeRegressor,
@@ -552,5 +564,5 @@ def test_repr_html_wraps():
 def test_deprecated_estimator_type(Estimator):
     # Assert that deprecated _estimator_type warns FutureWarning
     est = Estimator()
-    with pytest.warns(FutureWarning):
-        hasattr(est, "_estimator_type")
+    with pytest.warns(FutureWarning, match="estimator_type is deprecated"):
+        getattr(est, "_estimator_type")

From 108a661e1e58cde1978e9a9b28c6c95b0f92bb1b Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Juan=20Carlos=20Alfaro=20Jim=C3=A9nez?=
 <JuanCarlos.Alfaro@uclm.es>
Date: Sun, 5 Jul 2020 19:44:59 +0200
Subject: [PATCH 16/42] CLN Apply suggested changes

---
 sklearn/feature_selection/tests/test_rfe.py  |  8 ++++++++
 sklearn/model_selection/_search.py           |  2 +-
 sklearn/model_selection/tests/test_search.py | 17 +++++++++++++++++
 sklearn/pipeline.py                          |  3 ++-
 sklearn/tests/test_base.py                   | 13 +++++++------
 sklearn/tests/test_pipeline.py               | 16 ++++++++++++++++
 6 files changed, 51 insertions(+), 8 deletions(-)

diff --git a/sklearn/feature_selection/tests/test_rfe.py b/sklearn/feature_selection/tests/test_rfe.py
index 87dd30e08761f..635326bf99708 100644
--- a/sklearn/feature_selection/tests/test_rfe.py
+++ b/sklearn/feature_selection/tests/test_rfe.py
@@ -494,6 +494,14 @@ def test_multioutput(ClsRFE):
     rfe_test.fit(X, y)
 
 
+@pytest.mark.parametrize("Estimator,estimator_type",
+                         [(SVC, "classifier"), (SVR, "regressor")])
+def test_rfe_estimator_type_tag(Estimator, estimator_type):
+    # Assert that estimator_type tag is properly set
+    rfe = RFE(Estimator())
+    assert rfe._get_tags()["estimator_type"] == estimator_type
+
+
 # TODO: Remove in version 0.26
 def test_deprecated_estimator_type():
     # Assert that deprecated _estimator_type warns FutureWarning
diff --git a/sklearn/model_selection/_search.py b/sklearn/model_selection/_search.py
index 78253b6edd3fd..03114371a2f71 100644
--- a/sklearn/model_selection/_search.py
+++ b/sklearn/model_selection/_search.py
@@ -871,7 +871,7 @@ def _store(key_name, array, weights=None, splits=False, rank=False):
         return results
 
     def _more_tags(self):
-        return self.estimator._more_tags()
+        return self.estimator._get_tags()
 
 
 class GridSearchCV(BaseSearchCV):
diff --git a/sklearn/model_selection/tests/test_search.py b/sklearn/model_selection/tests/test_search.py
index fb18d36f3a9e8..e0b6d22b15f11 100644
--- a/sklearn/model_selection/tests/test_search.py
+++ b/sklearn/model_selection/tests/test_search.py
@@ -68,6 +68,8 @@
 from sklearn.linear_model import Ridge, SGDClassifier, LinearRegression
 from sklearn.experimental import enable_hist_gradient_boosting  # noqa
 from sklearn.ensemble import HistGradientBoostingClassifier
+from sklearn.mixture import BayesianGaussianMixture
+from sklearn.ensemble import IsolationForest
 
 from sklearn.model_selection.tests.common import OneTimeSplitter
 
@@ -1887,6 +1889,21 @@ def _fit_param_callable():
     model.fit(X_train, y_train, **fit_params)
 
 
+@pytest.mark.parametrize(
+    "Estimator,params,estimator_type",
+    [(DecisionTreeClassifier, {"max_depth": [5, 10]}, "classifier"),
+     (DecisionTreeRegressor, {"max_depth": [5, 10]}, "regressor"),
+     (KMeans, {"n_clusters": [5, 10]}, "clusterer"),
+     (BayesianGaussianMixture, {"n_components": [5, 10]}, "DensityEstimator"),
+     (IsolationForest, {"max_depth": [5, 10]}, "outlier_detector")]
+)
+@pytest.mark.parametrize("SearchCV", [GridSearchCV, RandomizedSearchCV])
+def test_estimator_type_tag(SearchCV, Estimator, params, estimator_type):
+    # Assert that estimator_type tag is properly set
+    search = SearchCV(Estimator(), params)
+    assert search._get_tags()["estimator_type"] == estimator_type
+
+
 # TODO: Remove in version 0.26
 @pytest.mark.parametrize("SearchCV", [GridSearchCV, RandomizedSearchCV])
 def test_deprecated_estimator_type(SearchCV):
diff --git a/sklearn/pipeline.py b/sklearn/pipeline.py
index 7af361b09cb6f..7ff43ef732901 100644
--- a/sklearn/pipeline.py
+++ b/sklearn/pipeline.py
@@ -643,7 +643,8 @@ def _get_name(name, est):
                             dash_wrapped=False)
 
     def _more_tags(self):
-        return self.steps[-1][1]._more_tags()
+        print(self.steps[-1][1])
+        return self.steps[-1][1]._get_tags()
 
 
 def _name_estimators(estimators):
diff --git a/sklearn/tests/test_base.py b/sklearn/tests/test_base.py
index 491f3dd39bcc6..5d028d99cbb0c 100644
--- a/sklearn/tests/test_base.py
+++ b/sklearn/tests/test_base.py
@@ -550,17 +550,18 @@ def test_repr_html_wraps():
                           (BayesianGaussianMixture, "DensityEstimator"),
                           (IsolationForest, "outlier_detector")])
 def test_estimator_type_tag(Estimator, estimator_type):
-    # Assert that the estimator_type tag is properly set
+    # Assert that estimator_type tag is properly set
     est = Estimator()
     assert est._get_tags()["estimator_type"] == estimator_type
 
 
 # TODO: Remove in version 0.26
-@pytest.mark.parametrize("Estimator", [DecisionTreeClassifier,
-                                       DecisionTreeRegressor,
-                                       KMeans,
-                                       BayesianGaussianMixture,
-                                       IsolationForest])
+@pytest.mark.parametrize("Estimator",
+                         [DecisionTreeClassifier,
+                          DecisionTreeRegressor,
+                          KMeans,
+                          BayesianGaussianMixture,
+                          IsolationForest])
 def test_deprecated_estimator_type(Estimator):
     # Assert that deprecated _estimator_type warns FutureWarning
     est = Estimator()
diff --git a/sklearn/tests/test_pipeline.py b/sklearn/tests/test_pipeline.py
index a763e8f94be78..ecaab3c67bd06 100644
--- a/sklearn/tests/test_pipeline.py
+++ b/sklearn/tests/test_pipeline.py
@@ -36,6 +36,10 @@
 from sklearn.feature_extraction.text import CountVectorizer
 from sklearn.experimental import enable_hist_gradient_boosting  # noqa
 from sklearn.ensemble import HistGradientBoostingClassifier
+from sklearn.tree import DecisionTreeClassifier
+from sklearn.tree import DecisionTreeRegressor
+from sklearn.mixture import BayesianGaussianMixture
+from sklearn.ensemble import IsolationForest
 
 iris = load_iris()
 
@@ -1222,6 +1226,18 @@ def transform(self, X, y=None):
     t.fit_transform(X, y, a=0)
 
 
+@pytest.mark.parametrize(
+    "Estimator,estimator_type", [(DecisionTreeClassifier, "classifier"),
+                                 (DecisionTreeRegressor, "regressor"),
+                                 (KMeans, "clusterer"),
+                                 (BayesianGaussianMixture, "DensityEstimator"),
+                                 (IsolationForest, "outlier_detector")])
+def test_estimator_type_tag(Estimator, estimator_type):
+    # Assert that estimator_type tag is properly set
+    pipeline = Pipeline([('est', Estimator())])
+    assert pipeline._get_tags()["estimator_type"] == estimator_type
+
+
 # TODO: Remove in version 0.26
 def test_deprecated_estimator_type():
     # Assert that deprecated _estimator_type warns FutureWarning

From dc18f3cc7a111e9e82ecbaa30c925573c4d42e3b Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Juan=20Carlos=20Alfaro=20Jim=C3=A9nez?=
 <JuanCarlos.Alfaro@uclm.es>
Date: Sun, 5 Jul 2020 19:47:37 +0200
Subject: [PATCH 17/42] MNT Minor changes

---
 sklearn/tests/test_base.py | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/sklearn/tests/test_base.py b/sklearn/tests/test_base.py
index 5d028d99cbb0c..0916748734b43 100644
--- a/sklearn/tests/test_base.py
+++ b/sklearn/tests/test_base.py
@@ -543,12 +543,12 @@ def test_repr_html_wraps():
         assert "<style>" in output
 
 
-@pytest.mark.parametrize("Estimator,estimator_type",
-                         [(DecisionTreeClassifier, "classifier"),
-                          (DecisionTreeRegressor, "regressor"),
-                          (KMeans, "clusterer"),
-                          (BayesianGaussianMixture, "DensityEstimator"),
-                          (IsolationForest, "outlier_detector")])
+@pytest.mark.parametrize(
+    "Estimator,estimator_type", [(DecisionTreeClassifier, "classifier"),
+                                 (DecisionTreeRegressor, "regressor"),
+                                 (KMeans, "clusterer"),
+                                 (BayesianGaussianMixture, "DensityEstimator"),
+                                 (IsolationForest, "outlier_detector")])
 def test_estimator_type_tag(Estimator, estimator_type):
     # Assert that estimator_type tag is properly set
     est = Estimator()

From ebf97c15a98a0366cd2e27e3c6e6a860d1f5db5d Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Juan=20Carlos=20Alfaro=20Jim=C3=A9nez?=
 <JuanCarlos.Alfaro@uclm.es>
Date: Sun, 5 Jul 2020 19:48:11 +0200
Subject: [PATCH 18/42] MNT Minor changes

---
 sklearn/tests/test_base.py | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/sklearn/tests/test_base.py b/sklearn/tests/test_base.py
index 0916748734b43..090b2e8b275ad 100644
--- a/sklearn/tests/test_base.py
+++ b/sklearn/tests/test_base.py
@@ -556,12 +556,12 @@ def test_estimator_type_tag(Estimator, estimator_type):
 
 
 # TODO: Remove in version 0.26
-@pytest.mark.parametrize("Estimator",
-                         [DecisionTreeClassifier,
-                          DecisionTreeRegressor,
-                          KMeans,
-                          BayesianGaussianMixture,
-                          IsolationForest])
+@pytest.mark.parametrize(
+    "Estimator", [DecisionTreeClassifier,
+                  DecisionTreeRegressor,
+                  KMeans,
+                  BayesianGaussianMixture,
+                  IsolationForest])
 def test_deprecated_estimator_type(Estimator):
     # Assert that deprecated _estimator_type warns FutureWarning
     est = Estimator()

From 34708010d80438ea8aacd84d17a23d77ebfa8929 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Juan=20Carlos=20Alfaro=20Jim=C3=A9nez?=
 <JuanCarlos.Alfaro@uclm.es>
Date: Mon, 6 Jul 2020 09:19:11 +0200
Subject: [PATCH 19/42] CLN Apply suggested changes

---
 sklearn/metrics/_plot/tests/test_plot_roc_curve.py |  2 +-
 sklearn/model_selection/tests/test_search.py       | 12 ++++++------
 sklearn/pipeline.py                                |  6 ++++--
 3 files changed, 11 insertions(+), 9 deletions(-)

diff --git a/sklearn/metrics/_plot/tests/test_plot_roc_curve.py b/sklearn/metrics/_plot/tests/test_plot_roc_curve.py
index ff77f7eb7a398..b1ea7650587f4 100644
--- a/sklearn/metrics/_plot/tests/test_plot_roc_curve.py
+++ b/sklearn/metrics/_plot/tests/test_plot_roc_curve.py
@@ -57,7 +57,7 @@ def test_plot_roc_curve_error_no_response(pyplot, data_binary, response_method,
                                           msg):
     X, y = data_binary
 
-    class MyClassifier(BaseEstimator, ClassifierMixin):
+    class MyClassifier(ClassifierMixin, BaseEstimator):
         def fit(self, X, y):
             self.classes_ = [0, 1]
             return self
diff --git a/sklearn/model_selection/tests/test_search.py b/sklearn/model_selection/tests/test_search.py
index e0b6d22b15f11..c3180e9b11dc2 100644
--- a/sklearn/model_selection/tests/test_search.py
+++ b/sklearn/model_selection/tests/test_search.py
@@ -1891,11 +1891,11 @@ def _fit_param_callable():
 
 @pytest.mark.parametrize(
     "Estimator,params,estimator_type",
-    [(DecisionTreeClassifier, {"max_depth": [5, 10]}, "classifier"),
-     (DecisionTreeRegressor, {"max_depth": [5, 10]}, "regressor"),
-     (KMeans, {"n_clusters": [5, 10]}, "clusterer"),
-     (BayesianGaussianMixture, {"n_components": [5, 10]}, "DensityEstimator"),
-     (IsolationForest, {"max_depth": [5, 10]}, "outlier_detector")]
+    [(DecisionTreeClassifier, {"max_depth": [2, 3]}, "classifier"),
+     (DecisionTreeRegressor, {"max_depth": [2, 3]}, "regressor"),
+     (KMeans, {"n_clusters": [2, 3]}, "clusterer"),
+     (BayesianGaussianMixture, {"n_components": [2, 3]}, "DensityEstimator"),
+     (IsolationForest, {"max_depth": [2, 3]}, "outlier_detector")]
 )
 @pytest.mark.parametrize("SearchCV", [GridSearchCV, RandomizedSearchCV])
 def test_estimator_type_tag(SearchCV, Estimator, params, estimator_type):
@@ -1908,6 +1908,6 @@ def test_estimator_type_tag(SearchCV, Estimator, params, estimator_type):
 @pytest.mark.parametrize("SearchCV", [GridSearchCV, RandomizedSearchCV])
 def test_deprecated_estimator_type(SearchCV):
     # Assert that deprecated _estimator_type warns FutureWarning
-    search = SearchCV(DecisionTreeClassifier(), {'max_depth': [5, 10]})
+    search = SearchCV(DecisionTreeClassifier(), {'max_depth': [2, 3]})
     with pytest.warns(FutureWarning, match="estimator_type is deprecated"):
         getattr(search, "_estimator_type")
diff --git a/sklearn/pipeline.py b/sklearn/pipeline.py
index 7ff43ef732901..6b61ea8823f6b 100644
--- a/sklearn/pipeline.py
+++ b/sklearn/pipeline.py
@@ -643,8 +643,10 @@ def _get_name(name, est):
                             dash_wrapped=False)
 
     def _more_tags(self):
-        print(self.steps[-1][1])
-        return self.steps[-1][1]._get_tags()
+        more_tags = {}
+        for _, estimator in self.steps:
+            more_tags.update(estimator._more_tags())
+        return more_tags
 
 
 def _name_estimators(estimators):

From e1ee07113aeb5d27c001e5b592425290c81c89d3 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Juan=20Carlos=20Alfaro=20Jim=C3=A9nez?=
 <JuanCarlos.Alfaro@uclm.es>
Date: Mon, 6 Jul 2020 15:16:32 +0200
Subject: [PATCH 20/42] CLN Apply suggested changes

---
 sklearn/base.py                              |  4 ++--
 sklearn/feature_selection/_rfe.py            |  2 +-
 sklearn/feature_selection/tests/test_rfe.py  |  9 +++++---
 sklearn/model_selection/tests/test_search.py | 16 +++++++-------
 sklearn/pipeline.py                          |  7 +++----
 sklearn/tests/test_base.py                   | 22 +++++++++++---------
 6 files changed, 32 insertions(+), 28 deletions(-)

diff --git a/sklearn/base.py b/sklearn/base.py
index f9c3ba960c1c9..8d5779abc440e 100644
--- a/sklearn/base.py
+++ b/sklearn/base.py
@@ -720,7 +720,7 @@ class DensityMixin:
                 "0.24 and will be removed in 0.26")
     @property
     def _estimator_type(self):
-        return "DensityEstimator"
+        return "density_estimator"
 
     def score(self, X, y=None):
         """Return the score of the model on the data X
@@ -739,7 +739,7 @@ def score(self, X, y=None):
         pass
 
     def _more_tags(self):
-        return {'estimator_type': 'DensityEstimator'}
+        return {'estimator_type': 'density_estimator'}
 
 
 class OutlierMixin:
diff --git a/sklearn/feature_selection/_rfe.py b/sklearn/feature_selection/_rfe.py
index 3615f19e4a94f..5e1eefe62cf26 100644
--- a/sklearn/feature_selection/_rfe.py
+++ b/sklearn/feature_selection/_rfe.py
@@ -369,7 +369,7 @@ def _more_tags(self):
         return {'poor_score': True,
                 'allow_nan': estimator_tags.get('allow_nan', True),
                 'requires_y': True,
-                'estimator_type': estimator_tags.get('estimator_type', None)}
+                'estimator_type': estimator_tags['estimator_type']}
 
 
 class RFECV(RFE):
diff --git a/sklearn/feature_selection/tests/test_rfe.py b/sklearn/feature_selection/tests/test_rfe.py
index 635326bf99708..8c2edfa57e8ac 100644
--- a/sklearn/feature_selection/tests/test_rfe.py
+++ b/sklearn/feature_selection/tests/test_rfe.py
@@ -280,7 +280,8 @@ def test_rfecv_grid_scores_size():
         assert rfecv.n_features_ >= min_features_to_select
 
 
-@ignore_warnings(category=FutureWarning)
+# TODO: Remove decorator in version 0.26
+# with the estimator_type attribute
 def test_rfe_estimator_tags():
     rfe = RFE(SVC(kernel='linear'))
     assert rfe._estimator_type == "classifier"
@@ -494,8 +495,10 @@ def test_multioutput(ClsRFE):
     rfe_test.fit(X, y)
 
 
-@pytest.mark.parametrize("Estimator,estimator_type",
-                         [(SVC, "classifier"), (SVR, "regressor")])
+@pytest.mark.parametrize(
+    "Estimator, estimator_type",
+    [(SVC, "classifier"),
+     (SVR, "regressor")])
 def test_rfe_estimator_type_tag(Estimator, estimator_type):
     # Assert that estimator_type tag is properly set
     rfe = RFE(Estimator())
diff --git a/sklearn/model_selection/tests/test_search.py b/sklearn/model_selection/tests/test_search.py
index c3180e9b11dc2..12637c76e75a0 100644
--- a/sklearn/model_selection/tests/test_search.py
+++ b/sklearn/model_selection/tests/test_search.py
@@ -1890,17 +1890,17 @@ def _fit_param_callable():
 
 
 @pytest.mark.parametrize(
-    "Estimator,params,estimator_type",
-    [(DecisionTreeClassifier, {"max_depth": [2, 3]}, "classifier"),
-     (DecisionTreeRegressor, {"max_depth": [2, 3]}, "regressor"),
-     (KMeans, {"n_clusters": [2, 3]}, "clusterer"),
-     (BayesianGaussianMixture, {"n_components": [2, 3]}, "DensityEstimator"),
-     (IsolationForest, {"max_depth": [2, 3]}, "outlier_detector")]
+    "Estimator, estimator_type",
+    [(DecisionTreeClassifier, "classifier"),
+     (DecisionTreeRegressor, "regressor"),
+     (KMeans, "clusterer"),
+     (BayesianGaussianMixture, "density_estimator"),
+     (IsolationForest, "outlier_detector")]
 )
 @pytest.mark.parametrize("SearchCV", [GridSearchCV, RandomizedSearchCV])
-def test_estimator_type_tag(SearchCV, Estimator, params, estimator_type):
+def test_estimator_type_tag(SearchCV, Estimator, estimator_type):
     # Assert that estimator_type tag is properly set
-    search = SearchCV(Estimator(), params)
+    search = SearchCV(Estimator(), {})
     assert search._get_tags()["estimator_type"] == estimator_type
 
 
diff --git a/sklearn/pipeline.py b/sklearn/pipeline.py
index 6b61ea8823f6b..0bbc59c6679b0 100644
--- a/sklearn/pipeline.py
+++ b/sklearn/pipeline.py
@@ -643,10 +643,9 @@ def _get_name(name, est):
                             dash_wrapped=False)
 
     def _more_tags(self):
-        more_tags = {}
-        for _, estimator in self.steps:
-            more_tags.update(estimator._more_tags())
-        return more_tags
+        return {
+            'estimator_type': self.steps[-1][1]._get_tags()['estimator_type']
+        }
 
 
 def _name_estimators(estimators):
diff --git a/sklearn/tests/test_base.py b/sklearn/tests/test_base.py
index 090b2e8b275ad..6992c7a6aa338 100644
--- a/sklearn/tests/test_base.py
+++ b/sklearn/tests/test_base.py
@@ -544,11 +544,12 @@ def test_repr_html_wraps():
 
 
 @pytest.mark.parametrize(
-    "Estimator,estimator_type", [(DecisionTreeClassifier, "classifier"),
-                                 (DecisionTreeRegressor, "regressor"),
-                                 (KMeans, "clusterer"),
-                                 (BayesianGaussianMixture, "DensityEstimator"),
-                                 (IsolationForest, "outlier_detector")])
+    "Estimator, estimator_type",
+    [(DecisionTreeClassifier, "classifier"),
+     (DecisionTreeRegressor, "regressor"),
+     (KMeans, "clusterer"),
+     (BayesianGaussianMixture, "density_estimator"),
+     (IsolationForest, "outlier_detector")])
 def test_estimator_type_tag(Estimator, estimator_type):
     # Assert that estimator_type tag is properly set
     est = Estimator()
@@ -557,11 +558,12 @@ def test_estimator_type_tag(Estimator, estimator_type):
 
 # TODO: Remove in version 0.26
 @pytest.mark.parametrize(
-    "Estimator", [DecisionTreeClassifier,
-                  DecisionTreeRegressor,
-                  KMeans,
-                  BayesianGaussianMixture,
-                  IsolationForest])
+    "Estimator",
+    [DecisionTreeClassifier,
+     DecisionTreeRegressor,
+     KMeans,
+     BayesianGaussianMixture,
+     IsolationForest])
 def test_deprecated_estimator_type(Estimator):
     # Assert that deprecated _estimator_type warns FutureWarning
     est = Estimator()

From b9d0015be3518760817162d40c3bc8494daaa433 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Juan=20Carlos=20Alfaro=20Jim=C3=A9nez?=
 <JuanCarlos.Alfaro@uclm.es>
Date: Thu, 16 Jul 2020 12:05:49 +0200
Subject: [PATCH 21/42] FIX Add BaseEstimator to MyClassifier

---
 sklearn/metrics/_plot/tests/test_plot_roc_curve.py | 1 +
 1 file changed, 1 insertion(+)

diff --git a/sklearn/metrics/_plot/tests/test_plot_roc_curve.py b/sklearn/metrics/_plot/tests/test_plot_roc_curve.py
index d2b2934a9614d..cd9e74a3a5da8 100644
--- a/sklearn/metrics/_plot/tests/test_plot_roc_curve.py
+++ b/sklearn/metrics/_plot/tests/test_plot_roc_curve.py
@@ -12,6 +12,7 @@
 from sklearn.linear_model import LogisticRegression
 from sklearn.model_selection import train_test_split
 from sklearn.base import ClassifierMixin
+from sklearn.base import BaseEstimator
 from sklearn.exceptions import NotFittedError
 from sklearn.pipeline import make_pipeline
 from sklearn.preprocessing import StandardScaler

From b36509afb3e623073e4d0c0bf0e9235ff551f77a Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Juan=20Carlos=20Alfaro=20Jim=C3=A9nez?=
 <JuanCarlos.Alfaro@uclm.es>
Date: Fri, 17 Jul 2020 12:20:37 +0200
Subject: [PATCH 22/42] FIX Implement _get_tags method in MockClassifier

---
 sklearn/model_selection/tests/test_search.py     |  9 +++++++--
 sklearn/model_selection/tests/test_validation.py | 15 +++++++++------
 2 files changed, 16 insertions(+), 8 deletions(-)

diff --git a/sklearn/model_selection/tests/test_search.py b/sklearn/model_selection/tests/test_search.py
index 12637c76e75a0..1a0a75d8bb779 100644
--- a/sklearn/model_selection/tests/test_search.py
+++ b/sklearn/model_selection/tests/test_search.py
@@ -114,6 +114,9 @@ def set_params(self, **params):
         self.foo_param = params['foo_param']
         return self
 
+    def _get_tags(self):
+        return {'estimator_type': 'classifier'}
+
 
 class LinearSVCNoScore(LinearSVC):
     """An LinearSVC classifier that has no score method."""
@@ -122,8 +125,10 @@ def score(self):
         raise AttributeError
 
 
-X = np.array([[-1, -1], [-2, -1], [1, 1], [2, 1]])
-y = np.array([1, 1, 2, 2])
+# The number of samples per class need to be greater than or equal
+# to the number of splits for stratified cross-validation routines
+X = np.array([[-1, -1], [-2, -1], [1, 1], [2, 1], [-2, 1], [-1, 2]])
+y = np.array([1, 1, 1, 2, 2, 2])
 
 
 def assert_grid_iter_equals_getitem(grid):
diff --git a/sklearn/model_selection/tests/test_validation.py b/sklearn/model_selection/tests/test_validation.py
index 1cb08cc13f767..4550193c6c0fe 100644
--- a/sklearn/model_selection/tests/test_validation.py
+++ b/sklearn/model_selection/tests/test_validation.py
@@ -223,15 +223,18 @@ def score(self, X=None, Y=None):
     def get_params(self, deep=False):
         return {'a': self.a, 'allow_nd': self.allow_nd}
 
+    def _get_tags(self):
+        return {'estimator_type': 'classifier'}
+
 
 # XXX: use 2D array, since 1D X is being detected as a single sample in
 # check_consistent_length
-X = np.ones((10, 2))
+X = np.ones((15, 2))
 X_sparse = coo_matrix(X)
-y = np.array([0, 0, 1, 1, 2, 2, 3, 3, 4, 4])
-# The number of samples per class needs to be > n_splits,
-# for StratifiedKFold(n_splits=3)
-y2 = np.array([1, 1, 1, 2, 2, 2, 3, 3, 3, 3])
+y = np.array([0, 0, 0, 1, 1, 1, 2, 2, 2, 3, 3, 3, 4, 4, 4])
+# The number of samples per class need to be greater than or equal
+# to the number of splits for stratified cross-validation routines
+y2 = np.array([1, 1, 1, 1, 1, 2, 2, 2, 2, 2, 3, 3, 3, 3, 3])
 P_sparse = coo_matrix(np.eye(5))
 
 
@@ -620,7 +623,7 @@ def assert_fit_params(clf):
                   'dummy_str': DUMMY_STR,
                   'dummy_obj': DUMMY_OBJ,
                   'callback': assert_fit_params}
-    cross_val_score(clf, X, y, fit_params=fit_params)
+    cross_val_score(clf, X, y2, fit_params=fit_params)
 
 
 def test_cross_val_score_score_func():

From 78b865531be53857b31603fcfda2de9e7d4e5daf Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Juan=20Carlos=20Alfaro=20Jim=C3=A9nez?=
 <JuanCarlos.Alfaro@uclm.es>
Date: Fri, 17 Jul 2020 12:55:14 +0200
Subject: [PATCH 23/42] CLN Apply suggested changes

---
 doc/developers/develop.rst                   |  7 ++++
 sklearn/base.py                              | 35 --------------------
 sklearn/feature_selection/_rfe.py            |  7 ----
 sklearn/feature_selection/tests/test_rfe.py  | 11 ------
 sklearn/model_selection/_search.py           |  7 ----
 sklearn/model_selection/tests/test_search.py |  9 -----
 sklearn/pipeline.py                          |  7 ----
 sklearn/tests/test_base.py                   | 15 ---------
 sklearn/tests/test_pipeline.py               |  8 -----
 9 files changed, 7 insertions(+), 99 deletions(-)

diff --git a/doc/developers/develop.rst b/doc/developers/develop.rst
index 9f8312f8b0e00..1f836fe4dd46c 100644
--- a/doc/developers/develop.rst
+++ b/doc/developers/develop.rst
@@ -484,6 +484,13 @@ estimator_type (default=None)
     etc. It is set by mixins such as :class:`~base.ClassifierMixin`, but needs
     to be more explicitly adopted on a :term:`meta-estimator`. Its value should
     usually be checked by way of a helper such as :func:`base.is_classifier`.
+    The available estimator types are:
+
+    - classifier (e.g. :class:`tree.DecisionTreeClassifier`)
+    - regressor (e.g. :class:`tree.DecisionTreeRegressor`)
+    - clusterer (e.g. :class:`cluster.KMeans`)
+    - density_estimator (e.g. :class:`mixture.BayesianGaussianMixture`)
+    - outlier_detector (e.g. :class:`ensemble.IsolationForest`)
 
 multilabel (default=False)
     whether the estimator supports multilabel output
diff --git a/sklearn/base.py b/sklearn/base.py
index 8d5779abc440e..8586769342af1 100644
--- a/sklearn/base.py
+++ b/sklearn/base.py
@@ -467,13 +467,6 @@ def _repr_mimebundle_(self, **kwargs):
 class ClassifierMixin:
     """Mixin class for all classifiers in scikit-learn."""
 
-    # mypy error: Decorated property not supported
-    @deprecated("_estimator_type is deprecated in "  # type: ignore
-                "0.24 and will be removed in 0.26")
-    @property
-    def _estimator_type(self):
-        return "classifier"
-
     def score(self, X, y, sample_weight=None):
         """
         Return the mean accuracy on the given test data and labels.
@@ -508,13 +501,6 @@ def _more_tags(self):
 class RegressorMixin:
     """Mixin class for all regression estimators in scikit-learn."""
 
-    # mypy error: Decorated property not supported
-    @deprecated("_estimator_type is deprecated in "  # type: ignore
-                "0.24 and will be removed in 0.26")
-    @property
-    def _estimator_type(self):
-        return "regressor"
-
     def score(self, X, y, sample_weight=None):
         """Return the coefficient of determination R^2 of the prediction.
 
@@ -567,13 +553,6 @@ def _more_tags(self):
 class ClusterMixin:
     """Mixin class for all cluster estimators in scikit-learn."""
 
-    # mypy error: Decorated property not supported
-    @deprecated("_estimator_type is deprecated in "  # type: ignore
-                "0.24 and will be removed in 0.26")
-    @property
-    def _estimator_type(self):
-        return "clusterer"
-
     def fit_predict(self, X, y=None):
         """
         Perform clustering on X and returns cluster labels.
@@ -715,13 +694,6 @@ def fit_transform(self, X, y=None, **fit_params):
 class DensityMixin:
     """Mixin class for all density estimators in scikit-learn."""
 
-    # mypy error: Decorated property not supported
-    @deprecated("_estimator_type is deprecated in "  # type: ignore
-                "0.24 and will be removed in 0.26")
-    @property
-    def _estimator_type(self):
-        return "density_estimator"
-
     def score(self, X, y=None):
         """Return the score of the model on the data X
 
@@ -745,13 +717,6 @@ def _more_tags(self):
 class OutlierMixin:
     """Mixin class for all outlier detection estimators in scikit-learn."""
 
-    # mypy error: Decorated property not supported
-    @deprecated("_estimator_type is deprecated in "  # type: ignore
-                "0.24 and will be removed in 0.26")
-    @property
-    def _estimator_type(self):
-        return "outlier_detector"
-
     def fit_predict(self, X, y=None):
         """Perform fit on X and returns labels for X.
 
diff --git a/sklearn/feature_selection/_rfe.py b/sklearn/feature_selection/_rfe.py
index 5e1eefe62cf26..db4b9d12f513e 100644
--- a/sklearn/feature_selection/_rfe.py
+++ b/sklearn/feature_selection/_rfe.py
@@ -150,13 +150,6 @@ def __init__(self, estimator, *, n_features_to_select=None, step=1,
         self.importance_getter = importance_getter
         self.verbose = verbose
 
-    # mypy error: Decorated property not supported
-    @deprecated("_estimator_type is deprecated in "  # type: ignore
-                "0.24 and will be removed in 0.26")
-    @property
-    def _estimator_type(self):
-        return self.estimator._estimator_type
-
     @property
     def classes_(self):
         return self.estimator_.classes_
diff --git a/sklearn/feature_selection/tests/test_rfe.py b/sklearn/feature_selection/tests/test_rfe.py
index 8c2edfa57e8ac..61974ed11bfbc 100644
--- a/sklearn/feature_selection/tests/test_rfe.py
+++ b/sklearn/feature_selection/tests/test_rfe.py
@@ -280,11 +280,8 @@ def test_rfecv_grid_scores_size():
         assert rfecv.n_features_ >= min_features_to_select
 
 
-# TODO: Remove decorator in version 0.26
-# with the estimator_type attribute
 def test_rfe_estimator_tags():
     rfe = RFE(SVC(kernel='linear'))
-    assert rfe._estimator_type == "classifier"
     # make sure that cross-validation is stratified
     iris = load_iris()
     score = cross_val_score(rfe, iris.data, iris.target)
@@ -503,11 +500,3 @@ def test_rfe_estimator_type_tag(Estimator, estimator_type):
     # Assert that estimator_type tag is properly set
     rfe = RFE(Estimator())
     assert rfe._get_tags()["estimator_type"] == estimator_type
-
-
-# TODO: Remove in version 0.26
-def test_deprecated_estimator_type():
-    # Assert that deprecated _estimator_type warns FutureWarning
-    rfe = RFE(SVC())
-    with pytest.warns(FutureWarning, match="estimator_type is deprecated"):
-        getattr(rfe, "_estimator_type")
diff --git a/sklearn/model_selection/_search.py b/sklearn/model_selection/_search.py
index 0271ded9bc173..9bc9a9b290ed9 100644
--- a/sklearn/model_selection/_search.py
+++ b/sklearn/model_selection/_search.py
@@ -420,13 +420,6 @@ def __init__(self, estimator, *, scoring=None, n_jobs=None,
         self.error_score = error_score
         self.return_train_score = return_train_score
 
-    # mypy error: Decorated property not supported
-    @deprecated("_estimator_type is deprecated in "  # type: ignore
-                "0.24 and will be removed in 0.26")
-    @property
-    def _estimator_type(self):
-        return self.estimator._estimator_type
-
     @property
     def _pairwise(self):
         # allows cross-validation to see 'precomputed' metrics
diff --git a/sklearn/model_selection/tests/test_search.py b/sklearn/model_selection/tests/test_search.py
index 9e38fe627d6bd..b9ec0a9335540 100644
--- a/sklearn/model_selection/tests/test_search.py
+++ b/sklearn/model_selection/tests/test_search.py
@@ -2035,12 +2035,3 @@ def test_estimator_type_tag(SearchCV, Estimator, estimator_type):
     # Assert that estimator_type tag is properly set
     search = SearchCV(Estimator(), {})
     assert search._get_tags()["estimator_type"] == estimator_type
-
-
-# TODO: Remove in version 0.26
-@pytest.mark.parametrize("SearchCV", [GridSearchCV, RandomizedSearchCV])
-def test_deprecated_estimator_type(SearchCV):
-    # Assert that deprecated _estimator_type warns FutureWarning
-    search = SearchCV(DecisionTreeClassifier(), {'max_depth': [2, 3]})
-    with pytest.warns(FutureWarning, match="estimator_type is deprecated"):
-        getattr(search, "_estimator_type")
diff --git a/sklearn/pipeline.py b/sklearn/pipeline.py
index 2bf2638787c5b..5820775a398c8 100644
--- a/sklearn/pipeline.py
+++ b/sklearn/pipeline.py
@@ -212,13 +212,6 @@ def __getitem__(self, ind):
             return self.named_steps[ind]
         return est
 
-    # mypy error: Decorated property not supported
-    @deprecated("_estimator_type is deprecated in "  # type: ignore
-                "0.24 and will be removed in 0.26")
-    @property
-    def _estimator_type(self):
-        return self.steps[-1][1]._estimator_type
-
     @property
     def named_steps(self):
         # Use Bunch object to improve autocomplete
diff --git a/sklearn/tests/test_base.py b/sklearn/tests/test_base.py
index 6992c7a6aa338..4861d479db3bc 100644
--- a/sklearn/tests/test_base.py
+++ b/sklearn/tests/test_base.py
@@ -554,18 +554,3 @@ def test_estimator_type_tag(Estimator, estimator_type):
     # Assert that estimator_type tag is properly set
     est = Estimator()
     assert est._get_tags()["estimator_type"] == estimator_type
-
-
-# TODO: Remove in version 0.26
-@pytest.mark.parametrize(
-    "Estimator",
-    [DecisionTreeClassifier,
-     DecisionTreeRegressor,
-     KMeans,
-     BayesianGaussianMixture,
-     IsolationForest])
-def test_deprecated_estimator_type(Estimator):
-    # Assert that deprecated _estimator_type warns FutureWarning
-    est = Estimator()
-    with pytest.warns(FutureWarning, match="estimator_type is deprecated"):
-        getattr(est, "_estimator_type")
diff --git a/sklearn/tests/test_pipeline.py b/sklearn/tests/test_pipeline.py
index ecaab3c67bd06..89023c765f779 100644
--- a/sklearn/tests/test_pipeline.py
+++ b/sklearn/tests/test_pipeline.py
@@ -1236,11 +1236,3 @@ def test_estimator_type_tag(Estimator, estimator_type):
     # Assert that estimator_type tag is properly set
     pipeline = Pipeline([('est', Estimator())])
     assert pipeline._get_tags()["estimator_type"] == estimator_type
-
-
-# TODO: Remove in version 0.26
-def test_deprecated_estimator_type():
-    # Assert that deprecated _estimator_type warns FutureWarning
-    pipeline = Pipeline([('est', LinearRegression())])
-    with pytest.warns(FutureWarning):
-        hasattr(pipeline, "_estimator_type")

From 3c55f676efea1b73264b68d6bd3835859c82054a Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Juan=20Carlos=20Alfaro=20Jim=C3=A9nez?=
 <JuanCarlos.Alfaro@uclm.es>
Date: Fri, 17 Jul 2020 13:05:17 +0200
Subject: [PATCH 24/42] FIX Fix linting issues

---
 sklearn/base.py                   | 1 -
 sklearn/feature_selection/_rfe.py | 1 -
 sklearn/pipeline.py               | 1 -
 3 files changed, 3 deletions(-)

diff --git a/sklearn/base.py b/sklearn/base.py
index 8586769342af1..d1c0c34719491 100644
--- a/sklearn/base.py
+++ b/sklearn/base.py
@@ -19,7 +19,6 @@
 from .utils.validation import check_array
 from .utils._estimator_html_repr import estimator_html_repr
 from .utils.validation import _deprecate_positional_args
-from .utils.deprecation import deprecated
 
 _DEFAULT_TAGS = {
     'non_deterministic': False,
diff --git a/sklearn/feature_selection/_rfe.py b/sklearn/feature_selection/_rfe.py
index db4b9d12f513e..51142baf71215 100644
--- a/sklearn/feature_selection/_rfe.py
+++ b/sklearn/feature_selection/_rfe.py
@@ -14,7 +14,6 @@
 from ..utils.metaestimators import _safe_split
 from ..utils.validation import check_is_fitted
 from ..utils.validation import _deprecate_positional_args
-from ..utils.deprecation import deprecated
 from ..base import BaseEstimator
 from ..base import MetaEstimatorMixin
 from ..base import clone
diff --git a/sklearn/pipeline.py b/sklearn/pipeline.py
index 5820775a398c8..ed2d3b2edf193 100644
--- a/sklearn/pipeline.py
+++ b/sklearn/pipeline.py
@@ -22,7 +22,6 @@
 from .utils import Bunch, _print_elapsed_time
 from .utils.validation import check_memory
 from .utils.validation import _deprecate_positional_args
-from .utils.deprecation import deprecated
 
 from .utils.metaestimators import _BaseComposition
 

From 03fbd61bae1dd330ed9bdc867d111cad68390978 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Juan=20Carlos=20Alfaro=20Jim=C3=A9nez?=
 <JuanCarlos.Alfaro@uclm.es>
Date: Fri, 17 Jul 2020 13:23:43 +0200
Subject: [PATCH 25/42] MNT Use shorten links

---
 doc/developers/develop.rst | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/doc/developers/develop.rst b/doc/developers/develop.rst
index 1f836fe4dd46c..54619038e90d4 100644
--- a/doc/developers/develop.rst
+++ b/doc/developers/develop.rst
@@ -486,11 +486,11 @@ estimator_type (default=None)
     usually be checked by way of a helper such as :func:`base.is_classifier`.
     The available estimator types are:
 
-    - classifier (e.g. :class:`tree.DecisionTreeClassifier`)
-    - regressor (e.g. :class:`tree.DecisionTreeRegressor`)
-    - clusterer (e.g. :class:`cluster.KMeans`)
-    - density_estimator (e.g. :class:`mixture.BayesianGaussianMixture`)
-    - outlier_detector (e.g. :class:`ensemble.IsolationForest`)
+    - classifier (e.g. :class:`~tree.DecisionTreeClassifier`)
+    - regressor (e.g. :class:`~tree.DecisionTreeRegressor`)
+    - clusterer (e.g. :class:`~cluster.KMeans`)
+    - density_estimator (e.g. :class:`~mixture.BayesianGaussianMixture`)
+    - outlier_detector (e.g. :class:`~ensemble.IsolationForest`)
 
 multilabel (default=False)
     whether the estimator supports multilabel output

From abb69bd657c8104ab629008536dd26692b8113b2 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Juan=20Carlos=20Alfaro=20Jim=C3=A9nez?=
 <JuanCarlos.Alfaro@uclm.es>
Date: Fri, 17 Jul 2020 13:49:08 +0200
Subject: [PATCH 26/42] FIX Fix remaining test issues

---
 sklearn/metrics/tests/test_score_objects.py |  3 +++
 sklearn/tests/test_pipeline.py              | 11 ++++++-----
 2 files changed, 9 insertions(+), 5 deletions(-)

diff --git a/sklearn/metrics/tests/test_score_objects.py b/sklearn/metrics/tests/test_score_objects.py
index 67900b7cb77c3..9a90c509b36f3 100644
--- a/sklearn/metrics/tests/test_score_objects.py
+++ b/sklearn/metrics/tests/test_score_objects.py
@@ -614,10 +614,13 @@ def test_multimetric_scorer_calls_method_once(scorers, expected_predict_count,
     predict_proba_func = Mock(return_value=proba)
     decision_function_func = Mock(return_value=pos_proba)
 
+    _get_tags_func = Mock(return_value=dict(estimator_type="classifier"))
+
     mock_est.fit = fit_func
     mock_est.predict = predict_func
     mock_est.predict_proba = predict_proba_func
     mock_est.decision_function = decision_function_func
+    mock_est._get_tags = _get_tags_func
 
     scorer_dict = _check_multimetric_scoring(LogisticRegression(), scorers)
     multi_scorer = _MultimetricScorer(**scorer_dict)
diff --git a/sklearn/tests/test_pipeline.py b/sklearn/tests/test_pipeline.py
index 89023c765f779..01c0fe1421421 100644
--- a/sklearn/tests/test_pipeline.py
+++ b/sklearn/tests/test_pipeline.py
@@ -1227,11 +1227,12 @@ def transform(self, X, y=None):
 
 
 @pytest.mark.parametrize(
-    "Estimator,estimator_type", [(DecisionTreeClassifier, "classifier"),
-                                 (DecisionTreeRegressor, "regressor"),
-                                 (KMeans, "clusterer"),
-                                 (BayesianGaussianMixture, "DensityEstimator"),
-                                 (IsolationForest, "outlier_detector")])
+    "Estimator,estimator_type",
+    [(DecisionTreeClassifier, "classifier"),
+     (DecisionTreeRegressor, "regressor"),
+     (KMeans, "clusterer"),
+     (BayesianGaussianMixture, "density_estimator"),
+     (IsolationForest, "outlier_detector")])
 def test_estimator_type_tag(Estimator, estimator_type):
     # Assert that estimator_type tag is properly set
     pipeline = Pipeline([('est', Estimator())])

From 3b5a3f8d12e54926f671e6194c86c15fa6cff6b4 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Juan=20Carlos=20Alfaro=20Jim=C3=A9nez?=
 <JuanCarlos.Alfaro@uclm.es>
Date: Fri, 17 Jul 2020 13:51:24 +0200
Subject: [PATCH 27/42] MNT Minor changes

---
 sklearn/metrics/tests/test_score_objects.py | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/sklearn/metrics/tests/test_score_objects.py b/sklearn/metrics/tests/test_score_objects.py
index 9a90c509b36f3..38f2eeb66f3f5 100644
--- a/sklearn/metrics/tests/test_score_objects.py
+++ b/sklearn/metrics/tests/test_score_objects.py
@@ -614,13 +614,13 @@ def test_multimetric_scorer_calls_method_once(scorers, expected_predict_count,
     predict_proba_func = Mock(return_value=proba)
     decision_function_func = Mock(return_value=pos_proba)
 
-    _get_tags_func = Mock(return_value=dict(estimator_type="classifier"))
+    get_tags_func = Mock(return_value=dict(estimator_type="classifier"))
 
     mock_est.fit = fit_func
     mock_est.predict = predict_func
     mock_est.predict_proba = predict_proba_func
     mock_est.decision_function = decision_function_func
-    mock_est._get_tags = _get_tags_func
+    mock_est._get_tags = get_tags_func
 
     scorer_dict = _check_multimetric_scoring(LogisticRegression(), scorers)
     multi_scorer = _MultimetricScorer(**scorer_dict)

From a1aa05c987860d5c8eb4572da4082e13b3e44e5d Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Juan=20Carlos=20Alfaro=20Jim=C3=A9nez?=
 <JuanCarlos.Alfaro@uclm.es>
Date: Thu, 13 Aug 2020 16:49:21 +0200
Subject: [PATCH 28/42] MNT Deprecate _estimator_type private property

---
 sklearn/base.py                              | 46 ++++++++++++++++++++
 sklearn/feature_selection/_rfe.py            | 10 +++++
 sklearn/feature_selection/tests/test_rfe.py  | 12 +++++
 sklearn/model_selection/_search.py           |  9 ++++
 sklearn/model_selection/tests/test_search.py | 14 ++++++
 sklearn/pipeline.py                          |  9 ++++
 sklearn/tests/test_base.py                   | 13 ++++++
 sklearn/tests/test_pipeline.py               | 12 +++++
 8 files changed, 125 insertions(+)

diff --git a/sklearn/base.py b/sklearn/base.py
index d1c0c34719491..76f3bc7ffd708 100644
--- a/sklearn/base.py
+++ b/sklearn/base.py
@@ -19,6 +19,7 @@
 from .utils.validation import check_array
 from .utils._estimator_html_repr import estimator_html_repr
 from .utils.validation import _deprecate_positional_args
+from ..utils.deprecation import deprecated
 
 _DEFAULT_TAGS = {
     'non_deterministic': False,
@@ -466,6 +467,15 @@ def _repr_mimebundle_(self, **kwargs):
 class ClassifierMixin:
     """Mixin class for all classifiers in scikit-learn."""
 
+    # TODO: Remove in version 0.26 when _estimator_type is deprecated
+    # mypy error: Decorated property not supported
+    @deprecated(  # type: ignore
+        "_estimator_type is deprecated and "
+        "will be removed in version 0.26")
+    @property
+    def _estimator_type(self):
+        return "classifier"
+
     def score(self, X, y, sample_weight=None):
         """
         Return the mean accuracy on the given test data and labels.
@@ -500,6 +510,15 @@ def _more_tags(self):
 class RegressorMixin:
     """Mixin class for all regression estimators in scikit-learn."""
 
+    # TODO: Remove in version 0.26 when _estimator_type is deprecated
+    # mypy error: Decorated property not supported
+    @deprecated(  # type: ignore
+        "_estimator_type is deprecated and "
+        "will be removed in version 0.26")
+    @property
+    def _estimator_type(self):
+        return "regressor"
+
     def score(self, X, y, sample_weight=None):
         """Return the coefficient of determination R^2 of the prediction.
 
@@ -552,6 +571,15 @@ def _more_tags(self):
 class ClusterMixin:
     """Mixin class for all cluster estimators in scikit-learn."""
 
+    # TODO: Remove in version 0.26 when _estimator_type is deprecated
+    # mypy error: Decorated property not supported
+    @deprecated(  # type: ignore
+        "_estimator_type is deprecated and "
+        "will be removed in version 0.26")
+    @property
+    def _estimator_type(self):
+        return "clusterer"
+
     def fit_predict(self, X, y=None):
         """
         Perform clustering on X and returns cluster labels.
@@ -693,6 +721,15 @@ def fit_transform(self, X, y=None, **fit_params):
 class DensityMixin:
     """Mixin class for all density estimators in scikit-learn."""
 
+    # TODO: Remove in version 0.26 when _estimator_type is deprecated
+    # mypy error: Decorated property not supported
+    @deprecated(  # type: ignore
+        "_estimator_type is deprecated and "
+        "will be removed in version 0.26")
+    @property
+    def _estimator_type(self):
+        return "DensityEstimator"
+
     def score(self, X, y=None):
         """Return the score of the model on the data X
 
@@ -716,6 +753,15 @@ def _more_tags(self):
 class OutlierMixin:
     """Mixin class for all outlier detection estimators in scikit-learn."""
 
+    # TODO: Remove in version 0.26 when _estimator_type is deprecated
+    # mypy error: Decorated property not supported
+    @deprecated(  # type: ignore
+        "_estimator_type is deprecated and "
+        "will be removed in version 0.26")
+    @property
+    def _estimator_type(self):
+        return "outlier_detector"
+
     def fit_predict(self, X, y=None):
         """Perform fit on X and returns labels for X.
 
diff --git a/sklearn/feature_selection/_rfe.py b/sklearn/feature_selection/_rfe.py
index 51142baf71215..ee21efbfffe7f 100644
--- a/sklearn/feature_selection/_rfe.py
+++ b/sklearn/feature_selection/_rfe.py
@@ -14,6 +14,7 @@
 from ..utils.metaestimators import _safe_split
 from ..utils.validation import check_is_fitted
 from ..utils.validation import _deprecate_positional_args
+from ..utils.deprecation import deprecated
 from ..base import BaseEstimator
 from ..base import MetaEstimatorMixin
 from ..base import clone
@@ -149,6 +150,15 @@ def __init__(self, estimator, *, n_features_to_select=None, step=1,
         self.importance_getter = importance_getter
         self.verbose = verbose
 
+    # TODO: Remove in version 0.26 when _estimator_type is deprecated
+    # mypy error: Decorated property not supported
+    @deprecated(  # type: ignore
+        "_estimator_type is deprecated and "
+        "will be removed in version 0.26")
+    @property
+    def _estimator_type(self):
+        return self.estimator_._estimator_type
+
     @property
     def classes_(self):
         return self.estimator_.classes_
diff --git a/sklearn/feature_selection/tests/test_rfe.py b/sklearn/feature_selection/tests/test_rfe.py
index 61974ed11bfbc..ba2b851b12839 100644
--- a/sklearn/feature_selection/tests/test_rfe.py
+++ b/sklearn/feature_selection/tests/test_rfe.py
@@ -287,6 +287,9 @@ def test_rfe_estimator_tags():
     score = cross_val_score(rfe, iris.data, iris.target)
     assert score.min() > .7
 
+    # TODO: Remove in version 0.26 when _estimator_type is deprecated
+    assert rfe._estimator_type == "classifier"
+
 
 def test_rfe_min_step():
     n_features = 10
@@ -492,6 +495,15 @@ def test_multioutput(ClsRFE):
     rfe_test.fit(X, y)
 
 
+# TODO: Remove in version 0.26 when _estimator_type is deprecated
+@pytest.mark.parametrize("Estimator", [SVC, SVR])
+def test_estimator_type_deprecated(Estimator):
+    # Assert that _estimator_type is deprecated
+    rfe = RFE(Estimator())
+    with pytest.warns(FutureWarning, match="_estimator_type is deprecated"):
+        getattr(rfe, "_estimator_type")
+
+
 @pytest.mark.parametrize(
     "Estimator, estimator_type",
     [(SVC, "classifier"),
diff --git a/sklearn/model_selection/_search.py b/sklearn/model_selection/_search.py
index 9bc9a9b290ed9..b4cb3d8da12c0 100644
--- a/sklearn/model_selection/_search.py
+++ b/sklearn/model_selection/_search.py
@@ -420,6 +420,15 @@ def __init__(self, estimator, *, scoring=None, n_jobs=None,
         self.error_score = error_score
         self.return_train_score = return_train_score
 
+    # TODO: Remove in version 0.26 when _estimator_type is deprecated
+    # mypy error: Decorated property not supported
+    @deprecated(  # type: ignore
+        "_estimator_type is deprecated and "
+        "will be removed in version 0.26")
+    @property
+    def _estimator_type(self):
+        return self.estimator_._estimator_type
+
     @property
     def _pairwise(self):
         # allows cross-validation to see 'precomputed' metrics
diff --git a/sklearn/model_selection/tests/test_search.py b/sklearn/model_selection/tests/test_search.py
index b9ec0a9335540..8113dac18edb9 100644
--- a/sklearn/model_selection/tests/test_search.py
+++ b/sklearn/model_selection/tests/test_search.py
@@ -2022,6 +2022,20 @@ def _fit_param_callable():
     model.fit(X_train, y_train, **fit_params)
 
 
+# TODO: Remove in version 0.26 when _estimator_type is deprecated
+@pytest.mark.parametrize("Estimator", [DecisionTreeClassifier,
+                                       DecisionTreeRegressor,
+                                       KMeans,
+                                       BayesianGaussianMixture,
+                                       IsolationForest])
+@pytest.mark.parametrize("SearchCV", [GridSearchCV, RandomizedSearchCV])
+def test_estimator_type_deprecated(SearchCV, Estimator):
+    # Assert that _estimator_type is deprecated
+    search = SearchCV(Estimator(), {})
+    with pytest.warns(FutureWarning, match="_estimator_type is deprecated"):
+        getattr(search, "_estimator_type")
+
+
 @pytest.mark.parametrize(
     "Estimator, estimator_type",
     [(DecisionTreeClassifier, "classifier"),
diff --git a/sklearn/pipeline.py b/sklearn/pipeline.py
index ed2d3b2edf193..e65155fb3b90a 100644
--- a/sklearn/pipeline.py
+++ b/sklearn/pipeline.py
@@ -211,6 +211,15 @@ def __getitem__(self, ind):
             return self.named_steps[ind]
         return est
 
+    # TODO: Remove in version 0.26 when _estimator_type is deprecated
+    # mypy error: Decorated property not supported
+    @deprecated(  # type: ignore
+        "_estimator_type is deprecated and "
+        "will be removed in version 0.26")
+    @property
+     def _estimator_type(self):
+         return self.steps[-1][1]._estimator_type
+
     @property
     def named_steps(self):
         # Use Bunch object to improve autocomplete
diff --git a/sklearn/tests/test_base.py b/sklearn/tests/test_base.py
index 4861d479db3bc..6b64b38aa110f 100644
--- a/sklearn/tests/test_base.py
+++ b/sklearn/tests/test_base.py
@@ -543,6 +543,19 @@ def test_repr_html_wraps():
         assert "<style>" in output
 
 
+# TODO: Remove in version 0.26 when _estimator_type is deprecated
+@pytest.mark.parametrize("Estimator", [DecisionTreeClassifier,
+                                       DecisionTreeRegressor,
+                                       KMeans,
+                                       BayesianGaussianMixture,
+                                       IsolationForest])
+def test_estimator_type_deprecated(Estimator):
+    # Assert that _estimator_type is deprecated
+    est = Estimator()
+    with pytest.warns(FutureWarning, match="_estimator_type is deprecated"):
+        getattr(est, "_estimator_type")
+
+
 @pytest.mark.parametrize(
     "Estimator, estimator_type",
     [(DecisionTreeClassifier, "classifier"),
diff --git a/sklearn/tests/test_pipeline.py b/sklearn/tests/test_pipeline.py
index 01c0fe1421421..a96f24e19648a 100644
--- a/sklearn/tests/test_pipeline.py
+++ b/sklearn/tests/test_pipeline.py
@@ -1226,6 +1226,18 @@ def transform(self, X, y=None):
     t.fit_transform(X, y, a=0)
 
 
+@pytest.mark.parametrize("Estimator", [DecisionTreeClassifier,
+                                       DecisionTreeRegressor,
+                                       KMeans,
+                                       BayesianGaussianMixture,
+                                       IsolationForest])
+def test_estimator_type_deprecated(Estimator):
+    # Assert that _estimator_type is deprecated
+    pipeline = Pipeline([('est', Estimator())])
+    with pytest.warns(FutureWarning, match="_estimator_type is deprecated"):
+        getattr(pipeline, "_estimator_type")
+
+
 @pytest.mark.parametrize(
     "Estimator,estimator_type",
     [(DecisionTreeClassifier, "classifier"),

From 2269a30b6df8411b2c5a79bfc30d79e2d2bf9e78 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Juan=20Carlos=20Alfaro=20Jim=C3=A9nez?=
 <JuanCarlos.Alfaro@uclm.es>
Date: Thu, 13 Aug 2020 16:52:07 +0200
Subject: [PATCH 29/42] FIX Minor changes

---
 sklearn/feature_selection/_rfe.py  | 2 +-
 sklearn/model_selection/_search.py | 2 +-
 sklearn/pipeline.py                | 5 +++--
 3 files changed, 5 insertions(+), 4 deletions(-)

diff --git a/sklearn/feature_selection/_rfe.py b/sklearn/feature_selection/_rfe.py
index ee21efbfffe7f..484619e33e272 100644
--- a/sklearn/feature_selection/_rfe.py
+++ b/sklearn/feature_selection/_rfe.py
@@ -157,7 +157,7 @@ def __init__(self, estimator, *, n_features_to_select=None, step=1,
         "will be removed in version 0.26")
     @property
     def _estimator_type(self):
-        return self.estimator_._estimator_type
+        return self.estimator._estimator_type
 
     @property
     def classes_(self):
diff --git a/sklearn/model_selection/_search.py b/sklearn/model_selection/_search.py
index b4cb3d8da12c0..75856fda10eb5 100644
--- a/sklearn/model_selection/_search.py
+++ b/sklearn/model_selection/_search.py
@@ -427,7 +427,7 @@ def __init__(self, estimator, *, scoring=None, n_jobs=None,
         "will be removed in version 0.26")
     @property
     def _estimator_type(self):
-        return self.estimator_._estimator_type
+        return self.estimator._estimator_type
 
     @property
     def _pairwise(self):
diff --git a/sklearn/pipeline.py b/sklearn/pipeline.py
index e65155fb3b90a..e59aeef8c946b 100644
--- a/sklearn/pipeline.py
+++ b/sklearn/pipeline.py
@@ -22,6 +22,7 @@
 from .utils import Bunch, _print_elapsed_time
 from .utils.validation import check_memory
 from .utils.validation import _deprecate_positional_args
+from ..utils import deprecated
 
 from .utils.metaestimators import _BaseComposition
 
@@ -217,8 +218,8 @@ def __getitem__(self, ind):
         "_estimator_type is deprecated and "
         "will be removed in version 0.26")
     @property
-     def _estimator_type(self):
-         return self.steps[-1][1]._estimator_type
+    def _estimator_type(self):
+        return self.steps[-1][1]._estimator_type
 
     @property
     def named_steps(self):

From 67ed0dc65e8a6c34c40ab2e700d8ff38039a07ed Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Juan=20Carlos=20Alfaro=20Jim=C3=A9nez?=
 <JuanCarlos.Alfaro@uclm.es>
Date: Thu, 13 Aug 2020 16:58:47 +0200
Subject: [PATCH 30/42] FIX Minor changes

---
 sklearn/base.py     | 2 +-
 sklearn/pipeline.py | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/sklearn/base.py b/sklearn/base.py
index 76f3bc7ffd708..33eb6d68ff433 100644
--- a/sklearn/base.py
+++ b/sklearn/base.py
@@ -19,7 +19,7 @@
 from .utils.validation import check_array
 from .utils._estimator_html_repr import estimator_html_repr
 from .utils.validation import _deprecate_positional_args
-from ..utils.deprecation import deprecated
+from .utils.deprecation import deprecated
 
 _DEFAULT_TAGS = {
     'non_deterministic': False,
diff --git a/sklearn/pipeline.py b/sklearn/pipeline.py
index e59aeef8c946b..c785bfc369e1f 100644
--- a/sklearn/pipeline.py
+++ b/sklearn/pipeline.py
@@ -22,7 +22,7 @@
 from .utils import Bunch, _print_elapsed_time
 from .utils.validation import check_memory
 from .utils.validation import _deprecate_positional_args
-from ..utils import deprecated
+from .utils import deprecated
 
 from .utils.metaestimators import _BaseComposition
 

From 1f24a7174a6c5c846600497eb32a0156d0493732 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Juan=20Carlos=20Alfaro=20Jim=C3=A9nez?=
 <JuanCarlos.Alfaro@uclm.es>
Date: Mon, 17 Aug 2020 23:27:34 +0200
Subject: [PATCH 31/42] FIX Minor changes

---
 sklearn/feature_selection/tests/test_rfe.py | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/sklearn/feature_selection/tests/test_rfe.py b/sklearn/feature_selection/tests/test_rfe.py
index ba2b851b12839..cfb9e50529053 100644
--- a/sklearn/feature_selection/tests/test_rfe.py
+++ b/sklearn/feature_selection/tests/test_rfe.py
@@ -280,6 +280,8 @@ def test_rfecv_grid_scores_size():
         assert rfecv.n_features_ >= min_features_to_select
 
 
+# TODO: Remove decorator in version 0.26 when _estimator_type is deprecated
+@pytest.mark.filterwarnings("ignore::FutureWarning")
 def test_rfe_estimator_tags():
     rfe = RFE(SVC(kernel='linear'))
     # make sure that cross-validation is stratified

From e386624b57d9f2ed3abc1f3a446bd7dd7d62a4e3 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Juan=20Carlos=20Alfaro=20Jim=C3=A9nez?=
 <JuanCarlos.Alfaro@uclm.es>
Date: Thu, 8 Oct 2020 19:26:32 +0200
Subject: [PATCH 32/42] FIX Add @property to biclusters_

---
 sklearn/base.py | 1 +
 1 file changed, 1 insertion(+)

diff --git a/sklearn/base.py b/sklearn/base.py
index 73935f6d4424b..36574b519c746 100644
--- a/sklearn/base.py
+++ b/sklearn/base.py
@@ -629,6 +629,7 @@ def _more_tags(self):
 class BiclusterMixin:
     """Mixin class for all bicluster estimators in scikit-learn."""
 
+    @property
     def biclusters_(self):
         """Convenient way to get row and column indicators together.
 

From ffa6756bba58c221b51c24a6754d371023d073bc Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Juan=20Carlos=20Alfaro=20Jim=C3=A9nez?=
 <JuanCarlos.Alfaro@uclm.es>
Date: Thu, 8 Oct 2020 19:27:39 +0200
Subject: [PATCH 33/42] FIX Add unwanted removed lines

---
 sklearn/base.py | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/sklearn/base.py b/sklearn/base.py
index 36574b519c746..512905f4dcb31 100644
--- a/sklearn/base.py
+++ b/sklearn/base.py
@@ -918,8 +918,10 @@ def _is_pairwise(estimator):
 
     - If the `_pairwise` attribute and the tag are present and consistent,
       then use the value and not issue a warning.
+    - If the `_pairwise` attribute and the tag are present and not
       consistent, use the `_pairwise` value and issue a deprecation
       warning.
+    - If only the `_pairwise` attribute is present and it is not False,
       issue a deprecation warning and use the `_pairwise` value.
 
     Parameters

From 2ecf9f949e5bcc4f294d10ec405b96b508b75573 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Juan=20Carlos=20Alfaro=20Jim=C3=A9nez?=
 <JuanCarlos.Alfaro@uclm.es>
Date: Thu, 8 Oct 2020 19:29:13 +0200
Subject: [PATCH 34/42] FIX Iter

---
 sklearn/model_selection/_search.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/sklearn/model_selection/_search.py b/sklearn/model_selection/_search.py
index 14ee76c2b572c..88fda715692ef 100644
--- a/sklearn/model_selection/_search.py
+++ b/sklearn/model_selection/_search.py
@@ -433,7 +433,7 @@ def __init__(self, estimator, *, scoring=None, n_jobs=None,
                 "version 0.24 and will be removed in 0.26.")
     @property
     def _estimator_type(self):
-        return self.estimator._get_tags()["estimator_type"]
+        return self.estimator._estimator_type
 
     def _more_tags(self):
         # allows cross-validation to see 'precomputed' metrics

From 67a533215f1db32edb4af7cf699f304f3be54926 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Juan=20Carlos=20Alfaro=20Jim=C3=A9nez?=
 <JuanCarlos.Alfaro@uclm.es>
Date: Thu, 8 Oct 2020 19:30:07 +0200
Subject: [PATCH 35/42] FIX Iter

---
 sklearn/model_selection/tests/test_search.py | 2 --
 1 file changed, 2 deletions(-)

diff --git a/sklearn/model_selection/tests/test_search.py b/sklearn/model_selection/tests/test_search.py
index 714cefec2146a..dbb0517fd7d21 100644
--- a/sklearn/model_selection/tests/test_search.py
+++ b/sklearn/model_selection/tests/test_search.py
@@ -69,8 +69,6 @@
 from sklearn.linear_model import Ridge, SGDClassifier, LinearRegression
 from sklearn.experimental import enable_hist_gradient_boosting  # noqa
 from sklearn.ensemble import HistGradientBoostingClassifier
-from sklearn.mixture import BayesianGaussianMixture
-from sklearn.ensemble import IsolationForest
 
 from sklearn.model_selection.tests.common import OneTimeSplitter
 

From 8f94407771338ed3f052f8cfe373b19242f471a7 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Juan=20Carlos=20Alfaro=20Jim=C3=A9nez?=
 <JuanCarlos.Alfaro@uclm.es>
Date: Thu, 8 Oct 2020 20:12:52 +0200
Subject: [PATCH 36/42] FIX Fix warning

---
 sklearn/base.py            | 2 +-
 sklearn/tests/test_base.py | 8 +++-----
 2 files changed, 4 insertions(+), 6 deletions(-)

diff --git a/sklearn/base.py b/sklearn/base.py
index 512905f4dcb31..b7d50c3e7f957 100644
--- a/sklearn/base.py
+++ b/sklearn/base.py
@@ -905,7 +905,7 @@ def _is_estimator_type(estimator, estimator_type):
         if estimator_type_attribute != estimator_type_tag:
             warnings.warn("_estimator_type attribute was deprecated in 0.24 "
                           "and will be removed in 0.26. Set the estimator "
-                          "tags of your estimator instead", FutureWarning)
+                          "tags of your estimator instead.", FutureWarning)
 
         return estimator_type_attribute == estimator_type
 
diff --git a/sklearn/tests/test_base.py b/sklearn/tests/test_base.py
index 437fb6a51a4f8..644b37071d275 100644
--- a/sklearn/tests/test_base.py
+++ b/sklearn/tests/test_base.py
@@ -596,7 +596,7 @@ class TruePairwise(FalsePairwise):
 
 # TODO: Remove in 0.26 when the _estimator_type attribute is removed
 def test_is_estimator_type():
-    # Test the is_estimator_type function
+    # Test the _is_estimator_type function
 
     # The _estimator_type attribute is not
     # consistent with the estimator_type tag
@@ -624,10 +624,8 @@ def _get_tags(self):
 
     estimator = NotTagClassifier()
 
-    with pytest.warns(None) as record:
-        assert not _is_estimator_type(estimator, "classifier")
-
-    assert not record
+    with pytest.warns(FutureWarning, match=msg):
+        assert _is_estimator_type(estimator, "classifier")
 
     # The estimator_type tag is present while the
     # _estimator_type attribute is not present

From a9acf2c8f8f4520f1b8a232800244af1b528bae0 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Juan=20Carlos=20Alfaro=20Jim=C3=A9nez?=
 <JuanCarlos.Alfaro@uclm.es>
Date: Thu, 8 Oct 2020 20:18:31 +0200
Subject: [PATCH 37/42] FIX Remove print statement

---
 sklearn/pipeline.py | 1 -
 1 file changed, 1 deletion(-)

diff --git a/sklearn/pipeline.py b/sklearn/pipeline.py
index 277cd7229860a..ac25a0a34b9e1 100644
--- a/sklearn/pipeline.py
+++ b/sklearn/pipeline.py
@@ -627,7 +627,6 @@ def classes_(self):
 
     def _more_tags(self):
         # check if first estimator expects pairwise input
-        print(self.steps)
         transformer_tags = self.steps[0][1]._get_tags()
         estimator_tags = self.steps[-1][1]._get_tags()
 

From 36b0bcda19e7f522ed98f6cfa203cd10b4c62771 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Juan=20Carlos=20Alfaro=20Jim=C3=A9nez?=
 <JuanCarlos.Alfaro@uclm.es>
Date: Thu, 8 Oct 2020 20:23:11 +0200
Subject: [PATCH 38/42] FIX Fix tests

---
 sklearn/pipeline.py | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/sklearn/pipeline.py b/sklearn/pipeline.py
index ac25a0a34b9e1..fb59aea35c33a 100644
--- a/sklearn/pipeline.py
+++ b/sklearn/pipeline.py
@@ -626,9 +626,13 @@ def classes_(self):
         return self.steps[-1][-1].classes_
 
     def _more_tags(self):
-        # check if first estimator expects pairwise input
-        transformer_tags = self.steps[0][1]._get_tags()
-        estimator_tags = self.steps[-1][1]._get_tags()
+        # Check if first estimator expects pairwise input
+        transformer = self.steps[0][1]
+        # The transformers may be None
+        transformer_tags = transformer._get_tags() if transformer else {}
+
+        estimator = self.steps[-1][1]
+        estimator_tags = estimator._get_tags()
 
         return {'pairwise': transformer_tags.get('pairwise', False),
                 'estimator_type': estimator_tags.get('estimator_type', None)}

From 41e1f96eb66d5b16bbc2c9f5f48aab68b1593544 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Juan=20Carlos=20Alfaro=20Jim=C3=A9nez?=
 <JuanCarlos.Alfaro@uclm.es>
Date: Tue, 13 Oct 2020 14:20:41 +0200
Subject: [PATCH 39/42] CLN Apply suggested changes

---
 doc/glossary.rst                                      | 1 -
 sklearn/feature_selection/tests/test_rfe.py           | 3 ++-
 sklearn/metrics/_plot/tests/test_plot_curve_common.py | 3 ++-
 sklearn/model_selection/tests/test_search.py          | 5 +++--
 sklearn/tests/test_pipeline.py                        | 2 +-
 5 files changed, 8 insertions(+), 6 deletions(-)

diff --git a/doc/glossary.rst b/doc/glossary.rst
index 7a70091ac804a..a54418fc3734d 100644
--- a/doc/glossary.rst
+++ b/doc/glossary.rst
@@ -363,7 +363,6 @@ General Concepts
                  adopted on a :term:`meta-estimator`.  Its value should usually be		
                  checked by way of a helper such as :func:`base.is_classifier`.
 
-                
                 .. deprecated:: 0.24
 
                 The `_estimator_type` attribute is deprecated in 0.24. From 0.26
diff --git a/sklearn/feature_selection/tests/test_rfe.py b/sklearn/feature_selection/tests/test_rfe.py
index 3e57b607f2bd4..aaefcb39947a1 100644
--- a/sklearn/feature_selection/tests/test_rfe.py
+++ b/sklearn/feature_selection/tests/test_rfe.py
@@ -492,6 +492,7 @@ def test_multioutput(ClsRFE):
     rfe_test.fit(X, y)
 
 
+# TODO: Remove in 0.26 when the _estimator_type attribute is removed
 def test_rfe_estimator_type_deprecated():
     # Assert that the _estimator_type attribute is deprecated
     rfe = RFE(SVC())
@@ -500,4 +501,4 @@ def test_rfe_estimator_type_deprecated():
            "version 0.24 and will be removed in 0.26.")
 
     with pytest.warns(FutureWarning, match=msg):
-        rfe._estimator_type
+        assert rfe._estimator_type == "classifier"
diff --git a/sklearn/metrics/_plot/tests/test_plot_curve_common.py b/sklearn/metrics/_plot/tests/test_plot_curve_common.py
index c3b56f1724372..c0ab40a49bfc5 100644
--- a/sklearn/metrics/_plot/tests/test_plot_curve_common.py
+++ b/sklearn/metrics/_plot/tests/test_plot_curve_common.py
@@ -1,5 +1,6 @@
 import pytest
 
+from sklearn.base import BaseEstimator
 from sklearn.base import ClassifierMixin
 from sklearn.base import clone
 from sklearn.compose import make_column_transformer
@@ -53,7 +54,7 @@ def test_plot_curve_error_no_response(
 ):
     X, y = data_binary
 
-    class MyClassifier(ClassifierMixin):
+    class MyClassifier(ClassifierMixin, BaseEstimator):
         def fit(self, X, y):
             self.classes_ = [0, 1]
             return self
diff --git a/sklearn/model_selection/tests/test_search.py b/sklearn/model_selection/tests/test_search.py
index dbb0517fd7d21..f1b80216aac57 100644
--- a/sklearn/model_selection/tests/test_search.py
+++ b/sklearn/model_selection/tests/test_search.py
@@ -2086,7 +2086,8 @@ def _fit_param_callable():
     model.fit(X_train, y_train, **fit_params)
 
 
-def test_rfe_estimator_type_deprecated():
+# TODO: Remove in 0.26 when the _estimator_type attribute is removed
+def test_search_cv_estimator_type_deprecated():
     # Assert that the _estimator_type attribute is deprecated
     estimator = SVC(kernel="linear")
     param_grid = {"gamma": ["scale", "auto"]}
@@ -2097,4 +2098,4 @@ def test_rfe_estimator_type_deprecated():
            "version 0.24 and will be removed in 0.26.")
 
     with pytest.warns(FutureWarning, match=msg):
-        search._estimator_type
+        assert search._estimator_type == "classifier"
diff --git a/sklearn/tests/test_pipeline.py b/sklearn/tests/test_pipeline.py
index 13553924db6df..d58981f3d0701 100644
--- a/sklearn/tests/test_pipeline.py
+++ b/sklearn/tests/test_pipeline.py
@@ -1274,4 +1274,4 @@ def test_rfe_estimator_type_deprecated():
            "version 0.24 and will be removed in 0.26.")
 
     with pytest.warns(FutureWarning, match=msg):
-        pipeline._estimator_type
+        assert pipeline._estimator_type == "classifier"

From 5aace6ce6e406dc1b18407ddc91b9b6cf031eba7 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Juan=20Carlos=20Alfaro=20Jim=C3=A9nez?=
 <JuanCarlos.Alfaro@uclm.es>
Date: Tue, 13 Oct 2020 21:00:56 +0200
Subject: [PATCH 40/42] FIX Fix linting issue

---
 sklearn/model_selection/_search.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/sklearn/model_selection/_search.py b/sklearn/model_selection/_search.py
index 0e6f578ab99b2..5be4d0cfd585c 100644
--- a/sklearn/model_selection/_search.py
+++ b/sklearn/model_selection/_search.py
@@ -440,7 +440,7 @@ def _more_tags(self):
         estimator_tags = self.estimator._get_tags()
         return {'pairwise': estimator_tags.get('pairwise', False),
                 'estimator_type': estimator_tags.get('estimator_type', None),
-                '_xfail_checks": {'check_supervised_y_2d':
+                '_xfail_checks': {'check_supervised_y_2d':
                                   'DataConversionWarning not caught'}}
 
     # TODO: Remove in 0.26

From 49859bfbc1b4c414eb9c88637eae49be74f97790 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Juan=20Carlos=20Alfaro=20Jim=C3=A9nez?=
 <JuanCarlos.Alfaro@uclm.es>
Date: Tue, 13 Oct 2020 21:43:35 +0200
Subject: [PATCH 41/42] FIX Fix tests

---
 sklearn/metrics/tests/test_score_objects.py | 1 +
 1 file changed, 1 insertion(+)

diff --git a/sklearn/metrics/tests/test_score_objects.py b/sklearn/metrics/tests/test_score_objects.py
index 2ed948ddb85fc..4705f82796028 100644
--- a/sklearn/metrics/tests/test_score_objects.py
+++ b/sklearn/metrics/tests/test_score_objects.py
@@ -630,6 +630,7 @@ def test_multimetric_scorer_calls_method_once(scorers, expected_predict_count,
     mock_est.predict = predict_func
     mock_est.predict_proba = predict_proba_func
     mock_est.decision_function = decision_function_func
+    mock_est.estimator_type = "classifier"
     mock_est._get_tags = get_tags_func
 
     # Add the classes that would be found during fit

From e26433a066955aec113912dd06859fc52fce5c50 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Juan=20Carlos=20Alfaro=20Jim=C3=A9nez?=
 <JuanCarlos.Alfaro@uclm.es>
Date: Tue, 13 Oct 2020 22:17:44 +0200
Subject: [PATCH 42/42] FIX Fix tests

---
 sklearn/metrics/tests/test_score_objects.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/sklearn/metrics/tests/test_score_objects.py b/sklearn/metrics/tests/test_score_objects.py
index 4705f82796028..0b573538e69cb 100644
--- a/sklearn/metrics/tests/test_score_objects.py
+++ b/sklearn/metrics/tests/test_score_objects.py
@@ -630,7 +630,7 @@ def test_multimetric_scorer_calls_method_once(scorers, expected_predict_count,
     mock_est.predict = predict_func
     mock_est.predict_proba = predict_proba_func
     mock_est.decision_function = decision_function_func
-    mock_est.estimator_type = "classifier"
+    mock_est._estimator_type = "classifier"
     mock_est._get_tags = get_tags_func
 
     # Add the classes that would be found during fit