code: def unarchive(self, channel_name):
          
          channel_id = self.get_channel_id(channel_name)
          self.params.update({
              'channel': channel_id,
              })
          return FromUrl('https://slack.com/api/channels.unarchive', self._requests)(data=self.params).post()
docs: https://api.slack.com/methods/channels.unarchive