tests

Fix all mypy notes #809

Job	Run time
collateral (diffcov)	5m 58s
test_cygwin (39, windows-latest)	15m 57s
collateral (docs)	1m 55s
test (3.9, ubuntu-latest)	4m 32s
test (3.9, macos-latest)	3m 54s
test (3.9, windows-latest)	13m 18s
test (3.13, ubuntu-latest)	5m 24s
test (3.13, macos-latest)	4m 56s
test (3.13, windows-latest)	12m 20s
test (3.10, ubuntu-latest)	4m 8s
test (3.11, ubuntu-latest)	4m 18s
test (3.12, ubuntu-latest)	5m 53s
test (3.14, ubuntu-latest)	6m 49s
test (pypy3.10, ubuntu-latest, stdlib)	15m 59s
test (ubuntu-latest, 3.10, stdlib)	4m 41s
integration-test	0s
check	1s
release	0s
	1h 50m 3s

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