}
  }

  @Override
  public boolean containsValue(Object value) {
    return delegate.containsValue(value);
  }

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

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

  @Override

    }
  }

  @Override
  public boolean containsValue(Object value) {
    return delegate.containsValue(value);
  }

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

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

  @Override

      }
    }

    transient @Nullable NavigableSet<K> descendingKeySet;

    @Override
    public NavigableSet<K> descendingKeySet() {
      synchronized (mutex) {
        if (descendingKeySet == null) {
          return descendingKeySet = Synchronized.navigableSet(delegate().descendingKeySet(), mutex);
        }
        return descendingKeySet;
      }
    }

      }
    }

    transient @Nullable NavigableSet<K> descendingKeySet;

    @Override
    public NavigableSet<K> descendingKeySet() {
      synchronized (mutex) {
        if (descendingKeySet == null) {
          return descendingKeySet = Synchronized.navigableSet(delegate().descendingKeySet(), mutex);
        }
        return descendingKeySet;
      }
    }

    }

    @Override
    public NavigableSet<K> navigableKeySet() {
      return new StandardNavigableKeySet();
    }

    @Override
    public NavigableSet<K> descendingKeySet() {
      return standardDescendingKeySet();
    }

    @Override
    public K firstKey() {
      return standardFirstKey();
    }

    @Override

    @Override
    public @Nullable K ceilingKey(@ParametricNullness K key) {
      return fromMap().ceilingKey(key);
    }

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

    @Override
    public NavigableMap<K, V2> descendingMap() {
      return transformEntries(fromMap().descendingMap(), transformer);
    }

    @Override

    @Override
    public @Nullable K ceilingKey(@ParametricNullness K key) {
      return fromMap().ceilingKey(key);
    }

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

    @Override
    public NavigableMap<K, V2> descendingMap() {
      return transformEntries(fromMap().descendingMap(), transformer);
    }

    @Override

    assertThat(map.headMap("two", false).values()).containsExactly(3, 5).inOrder();
    assertThat(map.headMap("two", false).descendingMap().values()).containsExactly(5, 3).inOrder();
    assertThat(map.descendingKeySet()).containsExactly("two", "three", "one").inOrder();

    assertEquals(mapEntry("one", 3), map.pollFirstEntry());
    assertEquals(mapEntry("two", 3), map.pollLastEntry());
    assertEquals(1, map.size());
  }

      return new NavigableKeySet(sortedMap());
    }

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

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

    @Override
    public NavigableMap<K, Collection<V>> subMap(
        @ParametricNullness K fromKey, @ParametricNullness K toKey) {

    assertThat(map.headMap("two", false).values()).containsExactly(3, 5).inOrder();
    assertThat(map.headMap("two", false).descendingMap().values()).containsExactly(5, 3).inOrder();
    assertThat(map.descendingKeySet()).containsExactly("two", "three", "one").inOrder();

    assertEquals(mapEntry("one", 3), map.pollFirstEntry());
    assertEquals(mapEntry("two", 3), map.pollLastEntry());
    assertEquals(1, map.size());
  }