@Override
  protected InputDataDiffBuilder<Key, Value> createDiffBuilder(int inputId, @Nullable Collection<Key> keys) {
    return new KeyCollectionInputDataDiffBuilder<>(inputId, keys != null ? keys : Collections.emptySet());
  }
@Override
  protected InputDataDiffBuilder<Key, Value> createDiffBuilder(int inputId, @Nullable Collection<Key> keys)