Polishing functions that return multiple types of containers

Discussion from !219 (merged):

• @apearce started a discussion: (+1 comment)

  I feel like a namedtuple is a better type here, as we don't want to express a mapping explicitly, just to give labels to the values. But I imagine this was already considered during the hackathon @rmatev @mstahl?

We have functions that return multiple transformations of a container-of-tracks, such that the caller can chose which format(s) they want. It would be nice if we didn't to make the caller chose, such that they could give the possibilities to some algorithm and the framework decides which type is needed. This might be possible once gaudi/Gaudi!951 (merged) is merged.