menu_proposal

There will be following classes with their parent classes and
the methods they will support

class MenuBar (BoxLayout):
    # This is a BoxLayout with horizontal orientation

    def add_widget (self, menu_item, index=0):
        """To add a MenuItem to MenuBar. This function will first check
           whether menu_item is a MenuItem or any other Widget"""

class Menu (Bubble):
    
    def add_widget (self, menu_item, index=0):
        """To add a MenuItem to MenuBar. This function will first check 
           whether menu_item is a MenuItem or any other Widget"""
    
    def attach_to_menu_item (self, menu_item):
        """This will attach self to menu_item. So, clicking on menu_item will
           display the Menu. One Menu could be attached with only one
           menu_item"""
    
    def detach_from_menu_item (self):
        """This will detach menu from the menu_item"""
    
    Events:
        on_activate: will be called when Menu is shown to the user.
        on_select: when any MenuItem from Menu is selected.
                   This is available in DropDown already.
        on_attach: when Menu is attached to the menu_item.
        on_detach: when Menu is detached from the menu_item.

class MenuItem (object):
    """This is an abstract class for MenuItem"""    

class MenuItemButton (MenuItem, Button):
class MenuItemButton (MenuItem, ToggleButton):
class MenuItemButton (MenuItem, CheckBox):

These classes already contains, their own required events

Normal procedure to create a Menu.
    Create a MenuBar
    Create a MenuItem and then add to MenuBar
    Create a Menu and attach it to MenuItem
    Create new MenuItems and add them to Menu