* forward to this implementation or a subclass thereof.
   *
   * @since 12.0
   */
  protected class StandardDescendingSet extends Sets.DescendingSet<E> {
    /** Constructor for use by subclasses. */
    public StandardDescendingSet() {
      super(ForwardingNavigableSet.this);
    }
  }

  @Override
  public Iterator<E> descendingIterator() {