🚨 Fix `Type of "Field" is partially unknown` with Pyright in `strict` mode

[mpyuglgwkxcmodyrpo]

See #1598 for discussion. I wanted to see if this would pass tests across the matrix (don't see why they wouldn't). I think this only applies to pyright in strict mode.

I can't edit lables, so someone should add the bug label or whatever else is relevant.

[mpyuglgwkxcmodyrpo]

This is a more suitable alternative to #1604 as it keeps the from __future__ import annotations line a the top of main.py, thus keeping python 3.9 support.

[youhogeon-meritz]

That's awesome!

I hope the version with these changes gets released soon.