code: def add_alt(self, alt_id, description):
          
          alt_line = '##ALT=<ID={0},Description="{1}">'.format(
              alt_id, description
          )
          logger.info("Adding alternative allele line to vcf: {0}".format(alt_line))
          self.parse_meta_data(alt_line)
          return
docs: Add a alternative allele format field line to the header.
  
          Arguments:
              alt_id (str): The id of the alternative line
              description (str): A description of the info line