code: async def unregister(self, channel, event, callback):
          
          channel = self.channel(channel, create=False)
          if channel:
              channel.unregister(event, callback)
              if not channel:
                  await channel.disconnect()
                  self.channels.pop(channel.name)
          return channel
docs: Safely unregister a callback from the list of ``event``
          callbacks for ``channel_name``.
  
          :param channel: channel name
          :param event: event name
          :param callback: callback to execute when event on channel occurs
          :return: a coroutine which results in the channel object where the
              ``callback`` was removed (if found)