}

    @Override
    public @Nullable T pollLast() {
      return standardPollLast();
    }

    @Override
    public SortedSet<T> headSet(T toElement) {
      return standardHeadSet(toElement);
    }

    @Override
    public SortedSet<T> tailSet(T fromElement) {
      return standardTailSet(fromElement);
    }
  }

  @AndroidIncompatible // test-suite builders

   * boolean)} method. If you override {@link #headSet(Object, boolean)}, you may wish to override
   * {@link #headSet(Object)} to forward to this implementation.
   */
  protected SortedSet<E> standardHeadSet(@ParametricNullness E toElement) {
    return headSet(toElement, false);
  }

  @Override
  public NavigableSet<E> tailSet(@ParametricNullness E fromElement, boolean inclusive) {

      return forward.tailSet(toElement, inclusive).descendingSet();
    }

    @Override
    public SortedSet<E> headSet(@ParametricNullness E toElement) {
      return standardHeadSet(toElement);
    }

    @Override
    public NavigableSet<E> tailSet(@ParametricNullness E fromElement, boolean inclusive) {
      return forward.headSet(fromElement, inclusive).descendingSet();
    }