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

        candidates =
            rangesByLowerBound
                .headMap(upperBoundWindow.upperEndpoint(), false)
                .descendingMap()
                .values();
      } else {
        candidates = rangesByLowerBound.descendingMap().values();
      }
      PeekingIterator<Range<C>> backingItr = peekingIterator(candidates.iterator());
      if (backingItr.hasNext()

      }
    }

    transient @Nullable NavigableMap<K, V> descendingMap;

    @Override
    public NavigableMap<K, V> descendingMap() {
      synchronized (mutex) {
        if (descendingMap == null) {
          return descendingMap = navigableMap(delegate().descendingMap(), mutex);
        }
        return descendingMap;
      }
    }

    @Override

    }

    @LazyInit private transient @Nullable UnmodifiableNavigableMap<K, V> descendingMap;

    @Override
    public NavigableMap<K, V> descendingMap() {
      UnmodifiableNavigableMap<K, V> result = descendingMap;
      return (result == null)
          ? descendingMap = new UnmodifiableNavigableMap<>(delegate.descendingMap(), this)
          : result;
    }

    @Override

      }
    }

    transient @Nullable NavigableMap<K, V> descendingMap;

    @Override
    public NavigableMap<K, V> descendingMap() {
      synchronized (mutex) {
        if (descendingMap == null) {
          return descendingMap = navigableMap(delegate().descendingMap(), mutex);
        }
        return descendingMap;
      }
    }

    @Override