docs: def __on_message(self, connection, sender, message):
          """
          Got a message from a channel
          """
          if message.strip() == '!bot send':
              cycle = itertools.cycle(string.digits)
              content = ''.join(next(cycle) for _ in range(100))
              self.send_message(sender, content)
  
          else:
              parts = message.split(':', 2)
              if not parts or parts[0] != 'HRLD':
                  return
  
              if parts[1] == 'BEGIN':
                  # Beginning of multi-line message
                  self._queue[parts[2]] = []
  
              elif parts[1] == 'END':
                  # End of multi-line message
                  content = ''.join(self._queue.pop(parts[2]))
                  self.__notify(sender, content)
  
              elif parts[1] == 'MSG':
                  # Single-line message
                  content = parts[2]
                  self.__notify(sender, content)
  
              else:
                  # Multi-line message continuation
                  uid = parts[1]
                  self._queue[uid].append(parts[2])