[PYTHON] Override Pycharm typeshed

Cached_property has been added to functools since python3.8, but it didn't appear as a candidate in PyCharm.

• python 3.8
• PyCharm 2019.2.5

PyCharm has a copy of typeshed because it's old

To reflect the latest typeshed, clone typeshed to the project directory and specify it as Source Root.

OK

reference)

• https://github.com/python/typeshed
• https://www.jetbrains.com/help/pycharm/type-hinting-in-product.html#typeshed