proto type for many to one type serialization #17507

Job	Run time
test (1.6, short, ubuntu-latest)	27m 29s
test (1.6, long, ubuntu-latest)	4m 18s
test (1.10, short, ubuntu-latest)	20m 33s
test (1.10, long, ubuntu-latest)	5m 6s
doctest (1.10, ubuntu-latest)	26m 24s
test (1.11-nightly, short, ubuntu-latest)	23m 23s
doctest (1.11-nightly, ubuntu-latest)	26m 26s
test (1.11-nightly, long, ubuntu-latest)	9m 3s
doctest (nightly, ubuntu-latest)	29m 34s
test (nightly, short, ubuntu-latest)	22m 16s
doctest (1.10, ubuntu-latest, depwarn=error)	27m 11s
test (nightly, long, ubuntu-latest)	8m 55s
doctest (1.10, macOS, RPTU)	13m 10s
test (1.10, short, ubuntu-latest, depwarn=error)	21m 2s
test (1.10, long, ubuntu-latest, depwarn=error)	5m 20s
test (1.10, short, macOS, RPTU)	7m 52s
test (1.10, long, macOS, RPTU)	7m 26s
test (1.10, book, ubuntu-latest)	2h 30m 17s
test (nightly, book, ubuntu-latest)	1h 1m 49s
	8h 17m 34s

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