Add test purported to capture the failure, but it still passes.

Author: jaraco

importlib_metadata/_meta.py

@@ -33,6 +33,10 @@ def json(self) -> Dict[str, Union[str, List[str]]]:
 class SimplePath(Protocol):
     """
     A minimal subset of pathlib.Path required by PathDistribution.
+
+    >>> import pathlib
+    >>> import typing
+    >>> _: SimplePath = typing.cast(pathlib.Path, None)
     """
 
     def joinpath(self) -> 'SimplePath':