Subscribe to MQ message with filter seem not works

[vdomos]

In a plugin, if I subscribe to a particular MQ message like 'device-stats' in this plugin example:

self.log.info(u"==> Subscribe to MQ 'device-stats' messages") 
self.add_mq_sub("device-stats")

# -------------------------------------------------------------------------------------------------
def on_message(self, msgid, content):               
    ''' Receive 'device-stats' messages
        msgid = 'device-stats'
        content = {u'timestamp': 1500937509, u'sensor_id': u'210', u'device_id': 32, u'stored_value': u'10240971'}
    '''
    self.log.debug(u"Receive MQ '%s' message: %s" % (msgid, format(content)))
    if msgid == 'device-stats':
        ...

The on_message function will receive other messages too:

2017-07-26 10:58:56,944 domogik-flowmeter DEBUG Receive MQ 'device-stats' message: {u'timestamp': 1501059536, u'sensor_id': u'444', u'device_id': 84, u'stored_value': u'0.0'}
2017-07-26 10:58:57,055 domogik-flowmeter DEBUG Receive MQ 'device-stats' message: {u'timestamp': 1501059536, u'sensor_id': u'452', u'device_id': 89, u'stored_value': u'0.0'}
2017-07-26 10:59:02,869 domogik-flowmeter DEBUG Receive MQ 'device.update' message: {u'client_id': u'plugin-flowmeter.hades', u'device_id': u'86'}
2017-07-26 10:59:02,971 domogik-flowmeter DEBUG Receive MQ 'device.update' message: {u'client_id': u'plugin-flowmeter.hades', u'device_id': u'86'}