tests

Fix all mypy notes #808

Job	Run time
test_cygwin (39, windows-latest)	14m 25s
test (3.9, ubuntu-latest)	4m 17s
collateral (diffcov)	5m 31s
test (3.9, macos-latest)	3m 42s
collateral (docs)	1m 51s
test (3.9, windows-latest)	11m 22s
test (3.13, ubuntu-latest)	5m 7s
test (3.13, macos-latest)	3m 45s
test (3.13, windows-latest)	13m 22s
test (3.10, ubuntu-latest)	4m 11s
test (3.11, ubuntu-latest)	4m 11s
test (3.12, ubuntu-latest)	5m 41s
test (3.14, ubuntu-latest)	6m 31s
test (pypy3.10, ubuntu-latest, stdlib)	17m 33s
test (ubuntu-latest, 3.10, stdlib)	4m 10s
integration-test	0s
check	1s
release	0s
	1h 45m 40s

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