Package is marked with `py.typed` but many files still don't have type annotations

in our project we use `disallow_untyped_calls = true` in mypy, and since the package isn't fully type-annotated we have to use `type: ignore` for this :(

specifically - we use classes from `generators.py`, but just by cruising through some files in the repo it seems that many files aren't really typed

is there a plan to type-annotate the rest of the files? are PRs welcome for this?