opt_onlyMap.scala

// case class Rel3(id: Int, vals: Option[Map[String, Set[Int]]])
val setm1 = Map(1 -> Some(Map("a" -> Set(1,2))))
val setm2 = Map(1 -> Some(Map("a" -> Set(2,3))))
val setm3 = Map(1 -> None)
val setm4 = Map(2 -> Some(Map("b" -> Set(5,6))))

val all = Set(setm1, setm2, setm3, setm4)
import scalaz._
import Scalaz._

all.reduce(_ |+| _)

// res0: scala.collection.immutable.Map[Int,Option[scala.collection.immutable.Map[String,scala.collection.immutable.Set[Int]]]] = Map(2 -> Some(Map(b -> Set(5, 6))), 1 -> Some(Map(a -> Set(1, 2, 3))))