<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def add_alt(self, alt_id, description):
 """ 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 """

        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