from a Seq of Maps produce a Map with values being Seqs.
from a Seq of Maps produce a Map with values being Seqs. Note that it is impossible to reverse this function because we lose track of which V came from which Map. Often used with a com.twitter.storehaus.FutureCollector on the inner value.
PivotEncoder to Map[InnerK, V] (vs Iterable[(InnerK, V)], as com.twitter.bijection.Pivot would provide).
create a Map from a Set of keys and a lookup function
Helpful transformations on maps and collections. These are combinators or transformers on collections that should probably be somewhere in the scala collection API, but are not.