abstract class Node(val name: String)
  case class Leaf(_name: String, value: String) extends Node(_name)
  case class InternalNode(_name: String, children: List[Node]) extends Node(_name)

  object Node {
    implicit def nodeShow[T <: Node]: Show[T] = new Show[T] {
      override def show(t: T): String = s"(${t.name.show})"
    }
  }