[Bug]: Python Pipeline Options Grandchildren Args

[manav-glean]

What happened?

Pipeline Options doesn't recursively get all args from children of its subclasses which means you can't effectively have extended inheritance of the PipelineOptions class in python which is very useful. The current hack around this is to subclass your custom parent class and PipelineOptions which is a bit redundant.

Issue Priority

Priority: 3 (minor)

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