code: @Override
    public long getLongCardinality() {
      long size = 0;
      for (int i = 0; i < this.highLowContainer.size(); i++) {
        size += this.highLowContainer.getContainerAtIndex(i).getCardinality();
      }
      return size;
    }
docs: Returns the number of distinct integers added to the bitmap (e.g., number of bits set).
  
  @return the cardinality