code: def sort_precursor(c, loci):
      data_loci = [[x, loci[x].chr, int(loci[x].start), int(loci[x].end), loci[x].strand, len(c.loci2seq[x])] for x in list(c.loci2seq.keys())]
      data_loci = sorted(data_loci, key=itemgetter(5), reverse=True)
      return data_loci