code: def rename(self, group_name, new_name):
          
          group_id = self.get_group_id(group_name)
          self.params.update({
              'channel': group_id,
              'name':    new_name,
              })
          return FromUrl('https://slack.com/api/groups.rename', self._requests)(data=self.params).post()
docs: https://api.slack.com/methods/groups.rename