* entrySet} of {@code descendingMap}. If you override {@code descendingMap}, you may wish to
   * override {@code pollFirstEntry} to forward to this implementation.
   */
  protected @Nullable Entry<K, V> standardPollLastEntry() {
    return Iterators.pollNext(descendingMap().entrySet().iterator());
  }

  @Override
  public NavigableMap<K, V> descendingMap() {
    return delegate().descendingMap();
  }

   * entrySet} of {@code descendingMap}. If you override {@code descendingMap}, you may wish to
   * override {@code pollFirstEntry} to forward to this implementation.
   */
  protected @Nullable Entry<K, V> standardPollLastEntry() {
    return Iterators.pollNext(descendingMap().entrySet().iterator());
  }

  @Override
  public NavigableMap<K, V> descendingMap() {
    return delegate().descendingMap();
  }

    return navigableKeySet();
  }

  @Override
  public NavigableSet<K> descendingKeySet() {
    return descendingMap().navigableKeySet();
  }

  @Override
  public NavigableMap<K, V> descendingMap() {
    return new DescendingMap();
  }

  private final class DescendingMap extends Maps.DescendingMap<K, V> {
    @Override
    NavigableMap<K, V> forward() {
      return AbstractNavigableMap.this;
    }

    return navigableKeySet();
  }

  @Override
  public NavigableSet<K> descendingKeySet() {
    return descendingMap().navigableKeySet();
  }

  @Override
  public NavigableMap<K, V> descendingMap() {
    return new DescendingMap();
  }

  private final class DescendingMap extends Maps.DescendingMap<K, V> {
    @Override
    NavigableMap<K, V> forward() {
      return AbstractNavigableMap.this;
    }

          ImmutableMap<Range<Integer>, Integer> descendingMap = rangeMap.asDescendingMapOfRanges();
          assertEquals(expectedAsMap, asMap);
          assertEquals(expectedAsMap, descendingMap);
          SerializableTester.reserializeAndAssert(asMap);
          SerializableTester.reserializeAndAssert(descendingMap);
          assertEquals(
              ImmutableList.copyOf(asMap.entrySet()).reverse(),

          ImmutableMap<Range<Integer>, Integer> descendingMap = rangeMap.asDescendingMapOfRanges();
          assertEquals(expectedAsMap, asMap);
          assertEquals(expectedAsMap, descendingMap);
          SerializableTester.reserializeAndAssert(asMap);
          SerializableTester.reserializeAndAssert(descendingMap);
          assertEquals(
              ImmutableList.copyOf(asMap.entrySet()).reverse(),

  }

  public void testDescendingMap() {
    NavigableMap<String, Integer> map = create();
    NavigableMap<String, Integer> descendingMap = map.descendingMap();
    assertTrue(descendingMap instanceof SynchronizedNavigableMap);
    assertThat(((SynchronizedNavigableMap<String, Integer>) descendingMap).mutex)
        .isSameInstanceAs(mutex);
  }

  public void testFirstEntry() {
    assertThat(create().firstEntry()).isNull();

        assertThat(navigableMap.headMap(key, inclusive).descendingMap().entrySet())
            .containsExactlyElementsIn(expected.headMap(key, inclusive).descendingMap().entrySet())
            .inOrder();
        assertThat(navigableMap.tailMap(key, inclusive).descendingMap().entrySet())
            .containsExactlyElementsIn(expected.tailMap(key, inclusive).descendingMap().entrySet())
            .inOrder();
      }
    }
  }

  @Override
  public ImmutableSortedMap<K, V> descendingMap() {
    // TODO(kevinb): The descendingMap is never actually cached at all. Either:
    //
    // - Cache it, and annotate the field with @LazyInit.
    // - Simplify the code below, and consider eliminating the field (b/287198172), which is also
    //   set by one of the constructors.
    ImmutableSortedMap<K, V> result = descendingMap;
    if (result == null) {

      entryIterator.remove();
      return immutableEntry(entry.getKey(), unmodifiableCollectionSubclass(output));
    }

    @Override
    public NavigableMap<K, Collection<V>> descendingMap() {
      return new NavigableAsMap(sortedMap().descendingMap());
    }

    @Override
    public NavigableSet<K> keySet() {
      return (NavigableSet<K>) super.keySet();
    }

    @Override