Add annotations for returned data (#972) #1036

Job	Run time
linters (3.9, ubuntu-latest)	1m 47s
Testing on Python 3.8 (ubuntu-latest)	1m 43s
Testing on Python 3.8 (macos-13)	3m 31s
Testing on Python 3.8 (windows-2019)	2m 26s
Testing on Python 3.9 (ubuntu-latest)	1m 42s
Testing on Python 3.9 (macos-13)	3m 20s
Testing on Python 3.9 (windows-2019)	2m 52s
Testing on Python 3.10 (ubuntu-latest)	1m 43s
Testing on Python 3.10 (macos-13)	2m 4s
Testing on Python 3.10 (windows-2019)	2m 17s
Testing on Python 3.11 (ubuntu-latest)	1m 42s
Testing on Python 3.11 (macos-13)	3m 23s
Testing on Python 3.11 (windows-2019)	2m 25s
Testing on Python 3.12 (ubuntu-latest)	2m 4s
Testing on Python 3.12 (macos-13)	3m 3s
Testing on Python 3.12 (windows-2019)	5m 30s
	41m 32s

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