Clarify behavior of CallbackRegistry.disconnect with nonexistent cids.

anntzer · anntzer · commit 97ba0608a97b · 2020-10-26T17:33:18.000+01:00
This behavior is actually relied upon in some parts of the codebase, so
let's just document it.
diff --git a/lib/matplotlib/cbook/__init__.py b/lib/matplotlib/cbook/__init__.py
@@ -199,7 +199,11 @@ def _remove_proxy(self, proxy, *, _is_finalizing=sys.is_finalizing):
                 del self._func_cid_map[signal]
 
     def disconnect(self, cid):
-        """Disconnect the callback registered with callback id *cid*."""
+        """
+        Disconnect the callback registered with callback id *cid*.
+
+        No error is raised if such a callback does not exist.
+        """
         for eventname, callbackd in list(self.callbacks.items()):
             try:
                 del callbackd[cid]
