code: def add_success(self, group=None, type_='', field='', description=''):
          
          group = group or '(200)'
          group = int(group.lower()[1:-1])
          self.retcode = self.retcode or group
          if group != self.retcode:
              raise ValueError('Two or more retcodes!')
          type_ = type_ or '{String}'
          p = Param(type_, field, description)
          self.params['responce'][p.field] = p
docs: parse and append a success data param