private static class BinaryNode {
    final int x;
    final Optional<BinaryNode> left;
    final Optional<BinaryNode> right;

    BinaryNode(int x, Optional<BinaryNode> left, Optional<BinaryNode> right) {
      this.x = x;
      this.left = left;
      this.right = right;
    }
  }

  enum Topology {
    BALANCED {
      @Override
      Optional<BinaryNode> createTree(int size, Random rng) {

                MutableModelNode componentNode = findOwner(binaryNode);
                ComponentSpecIdentifier id = getId(componentNode, name);
                return BaseBinarySpec.create(
                    publicType.getConcreteClass(),
                    implementationType.getConcreteClass(),
                    id,
                    binaryNode,
                    componentNode,