code: private static int metadata_end_cmp_(MetaData x, MetaData y) {
          return x.getEnd().compareTo(y.getEnd());
      }
docs: Comparator, in order to sort MetaData based on the end timestamp.
  
  @param x One of the MetaData to compare.
  @param y Another one of the MetaData to compare.
  @return Comparator result.