Made ARG keyword optional in PythonFunction as is required to pass tests #3056

Job	Run time
codecheck / codecheck	43m 23s
linux / linux (-doc-mpi-)	49m 27s
conda / conda (ubuntu-20.04)	11m 0s
linux / linux (-mpi-)	50m 51s
docker / docker (fedora39)	20m 3s
conda / conda (macos-12)	20m 48s
linux / linux (-coverage-mpi-)	1h 3m 5s
docker / docker (rocky8)	22m 9s
conda / conda (macos-14)	4m 22s
linux / linux (-debug-)	30m 13s
linux / linux (-debug-mpi-)	45m 29s
linux / linux (-intel-)	44m 59s
mac / macports (macos-12)	19m 36s
linux / linux (-pycv-mpi-)	19m 42s
mac / macsimple (macos-12)	9m 57s
mac / macports (macos-14)	8m 57s
mac / macsimple (macos-14)	5m 35s
mac / macports (+allmodules, macos-12)	27m 26s
	8h 17m 2s

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