[sesgoe]

Please listen to this advice for anyone giving this a go after reading these comments.

I was pretty green to the Python typing ecosystem when I started implementing it in our large pre-existing codebase, and I did not lean heavily enough on a `mypy` configuration that was module-specific.

It would have saved me a significant headache, and in hindsight, this seems like the main viable option for typing an old codebase effectively. This gets extremely gross when you have 300 or 400+ submodules across your codebase, but start small and work your way from the outside in if you want the best chance of success.