}

    @Override
    public @Nullable T higher(T e) {
      return standardHigher(e);
    }

    @Override
    public @Nullable T pollFirst() {
      return standardPollFirst();
    }

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

    @Override
    public SortedSet<T> headSet(T toElement) {

   * override {@link #iterator} you may wish to override {@link #pollFirst} to forward to this
   * implementation.
   */
  @CheckForNull
  protected E standardPollFirst() {
    return Iterators.pollNext(iterator());
  }

  @Override
  @CheckForNull
  public E pollLast() {
    return delegate().pollLast();
  }

  /**