* Have Element inherit from MutableSequence, which is more precise than Sequence.
* Remove unnecessary inherited methods (e.g., __getitem__).
* Correct extend() to take an Iterable. (Sequence was too specific.)
* Alphabetize the typing imports, for sanity.
posixpath.pyi did a '*' import of genericpath.pyi and then redefined
everything it imported. Removes the duplicate definitions from posixpath
and improves the ones in genericpath.
* Fix a few return types in stdlib/2/inspect.pyi.
* Rename _FrameRecord to _FrameInfo
* Correct some return types in itertools.pyi from Iterable to Iterator.
* Change types.pyi syntax that pytype can't parse.
* Remove types.pyi from the pytype blacklist.
* Fix a few return types in stdlib/2/inspect.pyi.
* Rename _FrameRecord to _FrameInfo
* Correct some return types in itertools.pyi from Iterable to Iterator.
* Change types.pyi syntax that pytype can't parse.
* Fix a few return types in stdlib/2/inspect.pyi.
* Rename _FrameRecord to _FrameInfo
* Correct some return types in itertools.pyi from Iterable to Iterator.