@Override
  public int tryEnumerate(byte @Nullable [] hash) throws IOException {
    checkValidHash(hash);

    int id = enumerator.tryEnumerate(hash);
    if (id == NULL_ID) {
      return id;
    }
    return enumeratorIdToHashId(id);
  }
@Override
  public int tryEnumerate(byte @Nullable [] hash)