mypy

gh-106318: Add examples for str.casefold() and str.lower() methods (#… #10037

Job	Run time
Run mypy on Tools/jit	20s
Run mypy on Lib/test/libregrtest	22s
Run mypy on Lib/_pyrepl	22s
Run mypy on Tools/build	20s
Run mypy on Tools/clinic	20s
Run mypy on Lib/tomllib	18s
Run mypy on Tools/check-c-api-docs	17s
Run mypy on Tools/peg_generator	21s
Run mypy on Tools/cases_generator	19s
	2m 59s

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