https://docs.python.org/zh-cn/3.7/library/typing.html
https://www.python.org/dev/peps/pep-0483/
https://www.python.org/dev/peps/pep-0484/
https://docs.python.org/zh-cn/3.7/library/typing.html
https://www.python.org/dev/peps/pep-0483/
https://www.python.org/dev/peps/pep-0484/