How to use the gmqtt.client.logger.debug function in gmqtt

def _on_fbns_connack(self, flags, returncode, data):
        if returncode != 0:
            desc = FBNSConnAckReturnCodes.get(returncode, 'Unknown')
            raise Exception('Connack returncode: {returncode} - {desc}'.format(**locals()))
        data = data.decode('utf8')
        logger.debug('[FBNS CONNACK] {data}'.format(**locals()))
        data = json.loads(data)
        self.on_fbns_auth(data)
        self._register()

def _on_fbns_message(self, payload):
        # It's instagram event
        logger.debug('[FBNS_MSG] {payload}'.format(**locals()))
        self.on_fbns_message(payload)

def _on_fbns_register(self, payload):
        # Sucsessuf registered in FBNS and we got notification token for Instagram API registration
        if payload.get('error', None):
            error = payload['error']
            raise Exception('FBNS Register error message: {error}'.format(**logger))
        token = payload.get('token')
        logger.debug('[REG_RESP_TOPIC] {token}'.format(**locals()))
        self.on_fbns_token(token)

def _keep_connection(self):
        super()._keep_connection()
        logger.debug('[KEEP ALIVE]')