Attempt fixing typing issues raised with `runtime_type_check=True` #1297

Job	Run time
prepare-env / prepare-env (3.9, releases-only)	4m 56s
prepare-env / prepare-env (3.9, upstream-dev)	5m 53s
prepare-env / prepare-env (3.10, releases-only)	5m 4s
prepare-env / prepare-env (3.10, upstream-dev)	7m 24s
run-tests (3.9, releases-only)	7m 1s
run-tests (3.9, upstream-dev)	7m 11s
run-tests (3.10, releases-only)	8m 20s
run-tests (3.10, upstream-dev)	8m 20s
	54m 9s

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