get_menubar
Description:
Returns the menu model for the menu bar of the application.
Parameters:
| this | 
           an application  | 
      
Returns:
| 
           the menubar for windows of the application  | 
      
Returns the menu model for the menu bar of the application.
| this | 
           an application  | 
      
| 
           the menubar for windows of the application  |