DelegatingPMap
class DelegatingPMap[K[_], V[_]](backing: Map[K[Any], V[Any]]) extends AbstractRMap[K, V] with PMap[K, V]
Only suitable for K that is invariant in its type parameter. Option and List keys are not suitable, for example, because None <:< Option[String] and None <: Option[Int].
class Object
trait Matchable
class Any