mypy

gh-151039: Fix a crash when `_datetime` types outlive `_datetime` mod… #21785

Job	Run time
Run mypy on Lib/tomllib	18s
Run mypy on Lib/test/libregrtest	17s
Run mypy on Tools/jit	18s
Run mypy on Lib/_pyrepl	22s
Run mypy on Tools/clinic	17s
Run mypy on Tools/build	17s
Run mypy on Tools/peg_generator	17s
Run mypy on Tools/cases_generator	18s
Run mypy on Tools/check-c-api-docs	19s
	2m 43s

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