code: def add_contig(self, contig_id, length):
          
          contig_line = '##contig=<ID={0},length={1}>'.format(
              contig_id, length
          )
          logger.info("Adding contig line to vcf: {0}".format(contig_line))
          self.parse_meta_data(contig_line)
          return
docs: Add a contig line to the header.
  
          Arguments:
              contig_id (str): The id of the alternative line
              length (str): A description of the info line