code: def unsubscribe(self, channel_name):
          
          if channel_name in self.channels:
              self.connection.send_event(
                  'pusher:unsubscribe', {
                      'channel': channel_name,
                  }
              )
              del self.channels[channel_name]
docs: Unsubscribe from a channel
  
          :param str channel_name: The name of the channel to unsubscribe from.