Codestyle: Type Hints (PEP 484)

[WhiteApfel]

I want to work on async read/write (WIP #303) and see that there are no type hints in the code. Is it appropriate to add type hints, or is it better to stick with the current style?

[WhiteApfel]

I do not claim to work on full coverage of type hints, but I would like at least new functions or changed code to have such a convenient option.

[jonasmalacofilho]

I think type hints are desirable, in general and in this specific project.

But I'm not sure it would be very useful to add them in just a few isolated places (and without our CI actually checking them).

[demberto]

I could work up on a PR, if one isn't already being worked on.