docs: public NotificationChain basicSetGuard(XExpression newGuard, NotificationChain msgs)
  	{
  		XExpression oldGuard = guard;
  		guard = newGuard;
  		if (eNotificationRequired())
  		{
  			ENotificationImpl notification = new ENotificationImpl(this, Notification.SET, SarlPackage.SARL_BEHAVIOR_UNIT__GUARD, oldGuard, newGuard);
  			if (msgs == null) msgs = notification; else msgs.add(notification);
  		}
  		return msgs;
  	}