Add type hints to all code

[KyleFromNVIDIA]

No description provided.

[jameslamb]

Thanks for doing this! Totally support it. Before I review.... did you intentionally skip adding return type hints on most functions? Is that planned for a follow-up PR? If so, I won't add comments about that here, other than the meta comment "most functions should have return type hints".

Adding -> None for functions that don't return anything does improve mypy's ability to catch bugs, by the way. I wrote this up a while ago to check my own understanding of that: https://gist.github.com/jameslamb/791021322f4bd448d478093e5c786f64

[KyleFromNVIDIA]

I only skipped return hints on functions that don't return anything (which is most of them). I'll go back and add -> None where applicable.

[jameslamb]

Thanks, I'm really glad we're doing this! Think it will help a lot. I went through all the changes in this PR, left a few more suggestions for your consideration.

[jameslamb]

Looks great, thanks for considering all the review comments. Appreciate you going through and doing this!