Test

Fix fill_value serialization issues #3250

Job	Run time
py=3.11-min_deps	5m 9s
py=3.13-upstream	5m 7s
doctests	1m 4s
os=ubuntu-latest, py=3.11, np=1.25, deps=minimal	5m 10s
os=ubuntu-latest, py=3.11, np=1.25, deps=optional	5m 9s
os=ubuntu-latest, py=3.11, np=2.1, deps=minimal	5m 10s
os=ubuntu-latest, py=3.11, np=2.1, deps=optional	5m 8s
os=ubuntu-latest, py=3.12, np=1.25, deps=minimal	5m 7s
os=ubuntu-latest, py=3.12, np=1.25, deps=optional	5m 8s
os=ubuntu-latest, py=3.12, np=2.1, deps=minimal	5m 8s
os=ubuntu-latest, py=3.12, np=2.1, deps=optional	5m 8s
os=ubuntu-latest, py=3.13, np=1.25, deps=minimal	5m 7s
os=ubuntu-latest, py=3.13, np=1.25, deps=optional	5m 6s
os=ubuntu-latest, py=3.13, np=2.1, deps=minimal	5m 7s
os=ubuntu-latest, py=3.13, np=2.1, deps=optional	5m 8s
os=macos-latest, py=3.11, np=1.25, deps=optional	5m 9s
os=macos-latest, py=3.13, np=2.1, deps=optional	5m 7s
os=windows-latest, py=3.11, np=1.25, deps=optional	4m 54s
os=windows-latest, py=3.13, np=2.1, deps=optional	4m 55s
Test complete	1s
	1h 33m 2s

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