docs: def _aggregrate_scores(its,tss,num_sentences):
      """rerank the two vectors by
      min aggregrate rank, reorder"""
      final = []
      for i,el in enumerate(its):
          for j, le in enumerate(tss):
              if el[2] == le[2]:
                  assert el[1] == le[1]
                  final.append((el[1],i+j,el[2]))
      _final = sorted(final, key = lambda tup: tup[1])[:num_sentences]
      return sorted(_final, key = lambda tup: tup[0])