private static RandomAccessIntContainer createContainerForInvertedIndex() {
    return new UpgradableRandomAccessIntContainer<>(
      INVERTED_INDEX_SIZE_THRESHOLD,
      () -> {
        return new IntHashSetAsRAIntContainer(Hash.DEFAULT_INITIAL_SIZE, Hash.DEFAULT_LOAD_FACTOR);
      },
      (container) -> {
        // calculate needed capacity so there are less memory allocations
        int maxId = 0;
        for (IntIdsIterator it = container.intIterator(); it.hasNext(); ) {
          int id = it.next();
          if (maxId < id) maxId = id;
        }
        return new BitSetAsRAIntContainer(maxId + 1);
      }
    );
  }
private static RandomAccessIntContainer createContainerForInvertedIndex()