How to use the pyads.NotificationAttrib function in pyads

def test_decorated_device_notification(self):

        plc = pyads.Connection(TEST_SERVER_AMS_NET_ID, TEST_SERVER_AMS_PORT)

        @plc.notification(pyads.PLCTYPE_INT)
        def callback(handle, name, timestamp, value):
            print (handle, name, timestamp, value)

        with plc:
            plc.add_device_notification("a", pyads.NotificationAttrib(20), callback)
            plc.write_by_name("a", 1, pyads.PLCTYPE_INT)

pyads.open_port()
        adr = pyads.get_local_address()
        pyads.close_port()

        self.assertIsNotNone(adr)
        self.assertIsNone(pyads.get_local_address())
        self.assertIsNone(pyads.read_state(adr))
        self.assertIsNone(pyads.read_device_info(adr))
        self.assertIsNone(
            pyads.read_write(adr, 1, 2, pyads.PLCTYPE_INT, 1, pyads.PLCTYPE_INT)
        )
        self.assertIsNone(pyads.read(adr, 1, 2, pyads.PLCTYPE_INT))
        self.assertIsNone(pyads.read_by_name(adr, "hello", pyads.PLCTYPE_INT))
        self.assertIsNone(
            pyads.add_device_notification(
                adr, "test", pyads.NotificationAttrib(4), lambda x: x
            )

def test_device_notification(self):
        def callback(notification, data):
            pass

        handle_name = "test"
        attr = pyads.NotificationAttrib(8)
        requests = self.test_server.request_history

        with self.plc:
            notification, user = self.plc.add_device_notification(
                handle_name, attr, callback
            )

            # Assert that Read/Write command was used to get the handle by name
            self.assert_command_id(requests[0], constants.ADSCOMMAND_READWRITE)
            # Assert that ADDDEVICENOTIFICATION was used to add device notification
            self.assert_command_id(requests[1], constants.ADSCOMMAND_ADDDEVICENOTE)

            self.plc.del_device_notification(notification, user)

        # Assert that ADDDEVICENOTIFICATION was used to add device notification
        self.assert_command_id(requests[2], constants.ADSCOMMAND_DELDEVICENOTE)

plc = pyads.Connection("127.0.0.1.1.1", 851)
        self.assertIsNone(plc.get_local_address())
        self.assertIsNone(plc.read_state())
        self.assertIsNone(plc.read_device_info())
        self.assertIsNone(plc.read_write(1, 2, pyads.PLCTYPE_INT, 1, pyads.PLCTYPE_INT))
        self.assertIsNone(plc.read(1, 2, pyads.PLCTYPE_INT))
        self.assertIsNone(plc.read_by_name("hello", pyads.PLCTYPE_INT))
        self.assertIsNone(plc.get_handle("hello"))
        self.assertIsNone(
            plc.read_structure_by_name(
                "hello", (("", pyads.PLCTYPE_BOOL, 1), ("", pyads.PLCTYPE_BOOL, 1))
            )
        )
        self.assertIsNone(
            plc.add_device_notification(
                "test", pyads.NotificationAttrib(4), lambda x: x
            )

def add_device_notification(self, name, plc_datatype, callback):
        """Add a notification to the ADS devices."""
        import pyads

        attr = pyads.NotificationAttrib(ctypes.sizeof(plc_datatype))

        with self._lock:
            try:
                hnotify, huser = self._client.add_device_notification(
                    name, attr, self._device_notification_callback
                )
            except pyads.ADSError as err:
                _LOGGER.error("Error subscribing to %s: %s", name, err)
            else:
                hnotify = int(hnotify)
                self._notification_items[hnotify] = NotificationItem(
                    hnotify, huser, name, plc_datatype, callback
                )

                _LOGGER.debug(
                    "Added device notification %d for variable %s", hnotify, name