Reference Issues/PRs

Fixes #28717, which is analogous to #23311, but for polars.

See also #25896.

What does this implement/fix? Explain your changes.

This fix is analogous to #23318. We identify when the predictors passed to DecisionBoundaryPlot.from_estimator is a polars DataFrame and refrain from converting it to a numpy array and stripping the column names.

Any other comments?

The way we do this is a bit awkward because we want to avoid importing polars. A nicer way to do this would be something like the following:

X_grid = pl.DataFrame({
    column: series
    for column, series in zip(X.columns, (xx0.ravel(), xx1.ravel()))
})

... but that would require import polars as pl.

Instead we drop the existing columns and add columns with the same names and the data from meshgrid.