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Last commit 5a7bf84 at: https://3cf779e6.typertiangolo.pages.dev

Ok this is ready for review @tiangolo.

TLDR decisions to take:

• Do we resolve issues with assert and cast statements (first few commits in this PR) or by using ignore statements (final commits & current state)? I think mostly in our repo's we've been resorting to ignore statements so far.
• If we want ignore statements, are we happy with ty: ignore? I'd prefer it because 1) ty doesn't support type: ignore with specific violations between brackets, and 2) if we use type: ignore, mypy will complain, and we'd have to put type: ignore[unused-ignore] which will work because of 1) but feels ugly/hacky.
• Do we want to resolve also ty warnings even if they don't fail the CI? (if yes, we can also enforce this via the CI with --error-on-warning