tests

Fix all the type errors mypy complains about #1159

Job	Run time
package-source	21s
py-3.8 lib-6.1 ubuntu-latest	5m 45s
package-wheel (macos-latest, arm64)	14m 40s
py-3.8 lib-6.0 ubuntu-latest	4m 34s
style	20s
package-wheel (macos-latest, x86_64)	27m 57s
py-3.8 lib-5.1 ubuntu-latest	4m 15s
package-wheel (ubuntu-latest, aarch64)	3h 30m 45s
py-3.8 lib-6.1 windows-latest	4m 41s
py-3.8 lib-5.0 ubuntu-latest	5m 37s
package-wheel (ubuntu-latest, i686)	22m 9s
py-3.8 lib-6.0 windows-latest	4m 18s
py-pypy3.9 lib-6.1 ubuntu-latest	4m 18s
package-wheel (ubuntu-latest, x86_64)	21m 3s
py-3.8 lib-5.1 windows-latest	4m 19s
py-3.8 lib-6.1 macos-latest	8m 17s
package-wheel (windows-latest, AMD64)	16m 58s
py-3.8 lib-5.0 windows-latest	3m 35s
publish	41s
	6h 4m 33s

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