human
Solve the following python programming problem given the following code:
def __init__(self, hass, name, state_topic, command_topic, qos, retain, state_open, state_closed, service_open, service_close, optimistic, value_template) : 
    'Initialize the garage door.' 
    self._hass = hass 
    self._name = name 
    self._state_topic = state_topic 
    self._command_topic = command_topic 
    self._qos = qos 
    self._retain = retain 
    self._state_open = state_open 
    self._state_closed = state_closed 
    self._service_open = service_open 
    self._service_close = service_close 
    self._optimistic = (optimistic or (state_topic is None)) 
    self._state = False 
    def message_received(topic, payload, qos) : 
        'A new MQTT message has been received.' 
        if (value_template is not None) : 
            payload = template.render_with_possible_json_value (hass, value_template, payload) 
if (payload == self._state_open) : 
            self._state = True 
            self.update_ha_state () 
else : 
            if (payload == self._state_closed) : 
                self._state = False 
                self.update_ha_state () 
if (self._state_topic is None) : 
        self._optimistic = True 
else : 
        mqtt.subscribe (hass, self._state_topic, <MASK>, self._qos) 
    
    Given the code above, what is a proper replacement for <MASK>?
assistant
#Here is a proper replacement for <MASK>.
def message_received(