code: def add_meta_line(self, key, value):
          
          meta_line = '##{0}={1}'.format(
              key, value
          )
          logger.info("Adding meta line to vcf: {0}".format(meta_line))
          self.parse_meta_data(meta_line)
          return
docs: Adds an arbitrary metadata line to the header.
  
          This must be a key value pair
  
          Arguments:
              key (str): The key of the metadata line
              value (str): The value of the metadata line