code: def call_later(self, delay, callback):
          
          if hasattr(self._connection.ioloop, "call_later"):
              self._connection.ioloop.call_later(delay, callback)
          else:
              self._connection.ioloop.add_timeout(delay, callback)
docs: Schedule a one-shot timeout given delay seconds.
  
          This method is only useful for compatibility with older versions of pika.
  
          Args:
              delay (float): Non-negative number of seconds from now until
                  expiration
              callback (method): The callback method, having the signature
                  `callback()`