Fix the new corrected bug

Oups, I did it again !!

libs/lib/xaal/lib/engine.py

@@ -28,7 +28,6 @@ from typing import Any, Optional
 from . import config, core
 from .exceptions import CallbackError, MessageParserError, XAALError
 from .network import NetworkConnector
-from .messages import MessageAction
 
 if typing.TYPE_CHECKING:
     from .devices import Device
@@ -119,7 +118,7 @@ class Engine(core.EngineMixin):
 
         targets = core.filter_msg_for_devices(msg, self.devices)
         for target in targets:
-            if msg.action == MessageAction.IS_ALIVE:
+            if msg.is_request_isalive():
                 self.send_alive(target)
             else:
                 self.handle_action_request(msg, target)