Add type annotations directly to clients

[tstirrat15]

Fixes #207

Description

This has been a pain point a couple of times now - I make some modification to the client files and forget to make associated updates to the stub files. I figure that adding the type annotations directly to the client file should satisfy mypy and prevent me from making that mistake again.

This should be generally fine, since our targeted python versions are compatible with type annotations.

Changes

• Add type annotations to the clients directly

  Testing

  Review.

[tstirrat15]

Hmm... This won't work because 3.8 and 3.9 don't support unioning abstract base classes. Oh well.