docs: def add_format(self, format_id, number, entry_type, description):
          """
          Add a format line to the header.
  
          Arguments:
              format_id (str): The id of the format line
              number (str): Integer or any of [A,R,G,.]
              entry_type (str): Any of [Integer,Float,Flag,Character,String]
              description (str): A description of the info line
  
          """
          format_line = '##FORMAT=<ID={0},Number={1},Type={2},Description="{3}">'.format(
              format_id, number, entry_type, description
          )
          logger.info("Adding format line to vcf: {0}".format(format_line))
          self.parse_meta_data(format_line)
          return