docs: public NotificationChain basicSetExpression(XExpression newExpression, NotificationChain msgs)
  	{
  		XExpression oldExpression = expression;
  		expression = newExpression;
  		if (eNotificationRequired())
  		{
  			ENotificationImpl notification = new ENotificationImpl(this, Notification.SET, SarlPackage.SARL_BEHAVIOR_UNIT__EXPRESSION, oldExpression, newExpression);
  			if (msgs == null) msgs = notification; else msgs.add(notification);
  		}
  		return msgs;
  	}