code: def sequencenames(contigsfile):
          
          sequences = list()
          for record in SeqIO.parse(open(contigsfile, "rU", encoding="iso-8859-15"), "fasta"):
              sequences.append(record.id)
          return sequences
docs: Takes a multifasta file and returns a list of sequence names
          :param contigsfile: multifasta of all sequences
          :return: list of all sequence names