code: def set_will(self, topic, payload, qos=0, retain=False):
          
          self.__mqtt.will_set(topic, payload, qos, retain=retain)
docs: Sets up the will message
  
          :param topic: Topic of the will message
          :param payload: Content of the message
          :param qos: Quality of Service
          :param retain: The message will be retained
          :raise ValueError: Invalid topic
          :raise TypeError: Invalid payload