Composing stateful and parallelizable transducers

[jtrakk]

@tkf wrote

Unfortunately, stateful transdcuers like Unique cannot be used after parallelizable transdcuer like ReducePartitonBy. It’s kind of a cost of parallelizability. There can be a better design to allow this but it’s a bit tricky to do ATM.

I think it would be useful to be able to compose these transducers, so I'm requesting that feature here.

[zsz00]

I think it would be useful to be able to compose these transducers, so I'm requesting that feature here.