}

  @Override
  public boolean containsAll(Collection<?> c) {
    return delegate.containsAll(c);
  }

  @Override
  public Iterator<E> descendingIterator() {
    return delegate.descendingIterator();
  }

  @Override
  public NavigableSet<E> descendingSet() {
    return new SafeTreeSet<>(delegate.descendingSet());
  }

  @Override
  public E first() {

  }

  @Override
  public UnmodifiableIterator<C> iterator() {
    return Iterators.emptyIterator();
  }

  @GwtIncompatible // NavigableSet
  @Override
  public UnmodifiableIterator<C> descendingIterator() {
    return Iterators.emptyIterator();
  }

  @Override
  boolean isPartialView() {
    return false;
  }

  @Override
  public boolean isEmpty() {
    return true;
  }

    }

    @Override
    public NavigableSet<E> descendingSet() {
      return new NavigableElementSet<>(multiset().descendingMultiset());
    }

    @Override
    public Iterator<E> descendingIterator() {
      return descendingSet().iterator();
    }

    @Override
    @CheckForNull
    public E pollFirst() {
      return getElementOrNull(multiset().pollFirstEntry());
    }

  }

  @Override
  public UnmodifiableIterator<C> iterator() {
    return Iterators.emptyIterator();
  }

  @GwtIncompatible // NavigableSet
  @Override
  public UnmodifiableIterator<C> descendingIterator() {
    return Iterators.emptyIterator();
  }

  @Override
  boolean isPartialView() {
    return false;
  }

  @Override
  public boolean isEmpty() {
    return true;
  }

    }

    @Override
    public NavigableSet<E> descendingSet() {
      return new NavigableElementSet<>(multiset().descendingMultiset());
    }

    @Override
    public Iterator<E> descendingIterator() {
      return descendingSet().iterator();
    }

    @Override
    @CheckForNull
    public E pollFirst() {
      return getElementOrNull(multiset().pollFirstEntry());
    }

    }

    @Override
    public Iterator<E> descendingIterator() {
      return Iterators.filter(unfiltered().descendingIterator(), predicate);
    }

    @Override
    @ParametricNullness
    public E last() {
      return Iterators.find(unfiltered().descendingIterator(), predicate);
    }

    @Override
    public NavigableSet<E> subSet(

        return equalsOrThrow(previous, last) ? null : domain.next(previous);
      }
    };
  }

  @GwtIncompatible // NavigableSet
  @Override
  public UnmodifiableIterator<C> descendingIterator() {
    return new AbstractSequentialIterator<C>(last()) {
      final C first = first();

      @Override
      @CheckForNull
      protected C computeNext(C previous) {

    }

    @Override
    public Iterator<E> descendingIterator() {
      return Iterators.filter(unfiltered().descendingIterator(), predicate);
    }

    @Override
    @ParametricNullness
    public E last() {
      return Iterators.find(unfiltered().descendingIterator(), predicate);
    }

    @Override
    public NavigableSet<E> subSet(

  @Override
  @CheckForNull
  public E lower(E e) {
    return Iterators.<@Nullable E>getNext(headSet(e, false).descendingIterator(), null);
  }

  /** @since 12.0 */
  @Override
  @CheckForNull
  public E floor(E e) {
    return Iterators.<@Nullable E>getNext(headSet(e, true).descendingIterator(), null);
  }

  /** @since 12.0 */
  @Override
  @CheckForNull
  public E ceiling(E e) {

      return wrap(getSortedSetDelegate().descendingSet());
    }

    @Override
    public Iterator<V> descendingIterator() {
      return new WrappedIterator(getSortedSetDelegate().descendingIterator());
    }

    @Override
    public NavigableSet<V> subSet(
        @ParametricNullness V fromElement,
        boolean fromInclusive,
        @ParametricNullness V toElement,