🚀 Feature

It is difficult to control the validity of function arguments when they are in different files.
Very often the information in *.pyi does not match *.py.

def optional_unwrap (self, x, y):
   # type: (Optional [int], Optional [int]) -> int

You can expand this format to indicate in which file to place annotations.
After that, all *.pyi can be completely assembled in one script. Information will always be up to date.

cc @ezyang @gchanan @zou3519