}

  @GwtIncompatible // NavigableMap
  private static final class NavigableAsMapView<
          K extends @Nullable Object, V extends @Nullable Object>
      extends AbstractNavigableMap<K, V> {
    /*
     * Using AbstractNavigableMap is simpler than extending SortedAsMapView and rewriting all the
     * NavigableMap methods.
     */

    private final NavigableSet<K> set;