cats.syntax
Foldable.foldK. Example:
scala> import cats.std.list._ scala> import cats.std.set._ scala> import cats.syntax.foldable._ scala> val l: List[Set[Int]] = List(Set(1, 2), Set(2, 3), Set(3, 4)) scala> l.foldK res0: Set[Int] = Set(1, 2, 3, 4)