public @Nullable List<Hash> getParents(int index) {
    return executeAndCatch(() -> {
      int[] parentsIndexes = myIndexStorageBackend.getParents(index);
      if (parentsIndexes == null) return null;
      return getHashes(myLogStorage, parentsIndexes);
    });
  }
public @Nullable List<Hash> getParents(int index)