}

  @Override
  public Comparator<? super E> comparator() {
    return delegate().comparator();
  }

  @Override
  SortedSet<E> createElementSet() {
    return Collections.unmodifiableSortedSet(delegate().elementSet());
  }

  @Override
  public SortedSet<E> elementSet() {
    return (SortedSet<E>) super.elementSet();
  }