Hey all, I was poking around and looking at `Distinct` and was confused about why it was implemented the way it was.
Reproduced here: @ptransform_fn @typehints.with_input_types(T) @typehints.with_output_types(T) def Distinct(pcoll): # pylint: disable=invalid-name """Produces a PCollection containing distinct elements of a PCollection.""" return ( pcoll | 'ToPairs' >> Map(lambda v: (v, None)) | 'Group' >> CombinePerKey(lambda vs: None) | 'Distinct' >> Keys()) Could anyone clarify why we'd use a `CombinePerKey` instead of just using `GroupByKey`? Cheers, Joey