code: def _find_rule_no(self, mac):
          
  
          ipt_cmd = ['iptables', '-L', '--line-numbers']
          cmdo = dsl.execute(ipt_cmd, self._root_helper, log_output=False)
          for o in cmdo.split('\n'):
              if mac in o.lower():
                  rule_no = o.split()[0]
                  LOG.info('Found rule %(rule)s for %(mac)s.',
                           {'rule': rule_no, 'mac': mac})
                  return rule_no
docs: Find rule number associated with a given mac.