PipelineDemultiplexerStage takes a property which is a list of {pipeline, predicate} representing pipelines to demultiplex into along with strategies determining which items should be sent to each. This is currently represented using Pair but it would be much better to use a custom nested record type: they are never modified, and the fields may never be null.

For 0.10, I’d like the existing code to work with a deprecation. That’s fairly easy to do as long as we change the property name: the old methods can simply construct calls to the new ones on the fly. I’d like to pull that in 1.0, though, so “deprecated for removal”.