Preserve values #193

Job	Run time
mypy (3.7)	29s
test (3.7, ubuntu-latest)	1m 1s
mypy (3.8)	34s
test (3.7, windows-latest)	2m 12s
mypy (3.9)	27s
test (3.7, macos-latest)	1m 40s
mypy (3.10)	35s
test (3.8, ubuntu-latest)	57s
mypy (3.11)	25s
test (3.8, windows-latest)	3m 10s
mypy (3.12)	37s
test (3.8, macos-latest)	1m 11s
test (3.9, ubuntu-latest)	1m 4s
test (3.9, windows-latest)	2m 4s
test (3.9, macos-latest)	1m 49s
test (3.10, ubuntu-latest)	1m 5s
test (3.10, windows-latest)	2m 38s
test (3.10, macos-latest)	1m 20s
test (3.11, ubuntu-latest)	54s
test (3.11, windows-latest)	2m 23s
test (3.11, macos-latest)	1m 6s
test (3.12, ubuntu-latest)	1m 39s
test (3.12, windows-latest)	3m 0s
test (3.12, macos-latest)	2m 51s
combine coverage and check for 100%	13s
	35m 24s

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