}
    };
  }

  static class TransformedEntriesMap<
          K extends @Nullable Object, V1 extends @Nullable Object, V2 extends @Nullable Object>
      extends IteratorBasedAbstractMap<K, V2> {
    final Map<K, V1> fromMap;
    final EntryTransformer<? super K, ? super V1, V2> transformer;

    TransformedEntriesMap(