private final NavigableSet<E> forward;

    DescendingSet(NavigableSet<E> forward) {
      this.forward = forward;
    }

    @Override
    protected NavigableSet<E> delegate() {
      return forward;
    }

    @Override
    @CheckForNull
    public E lower(@ParametricNullness E e) {
      return forward.higher(e);
    }

    @Override

      @SuppressWarnings("unchecked") // safe since map is not writable
      ImmutableBiMap<K, V> bimap = (ImmutableBiMap<K, V>) map;
      // TODO(lowasser): if we need to make a copy of a BiMap because the
      // forward map is a view, don't make a copy of the non-view delegate map
      if (!bimap.isPartialView()) {
        return bimap;
      }
    }
    return copyOf(map.entrySet());
  }

  /**

 * Undefined behavior and bugs will result.
 *
 * <p>See the Guava User Guide article on <a href=
 * "https://github.com/google/guava/wiki/ImmutableCollectionsExplained">immutable collections</a>.
 *
 * @author Mike Ward
 * @since 2.0
 */
@GwtCompatible(serializable = true, emulated = true)
@ElementTypesAreNonnullByDefault
public class ImmutableSetMultimap<K, V> extends ImmutableMultimap<K, V>
    implements SetMultimap<K, V> {
  /**

   * of {@code iterator2}.
   *
   * <p>Note that this will modify the supplied iterators, since they will have been advanced some
   * number of elements forward.
   */
  public static boolean elementsEqual(Iterator<?> iterator1, Iterator<?> iterator2) {
    while (iterator1.hasNext()) {
      if (!iterator2.hasNext()) {
        return false;
      }

      return Ordering.from(forward).reverse();
    }

    @Override
    @ParametricNullness
    public K firstKey() {
      return forward().lastKey();
    }

    @Override
    @ParametricNullness
    public K lastKey() {
      return forward().firstKey();
    }

    @Override
    @CheckForNull