class User(object):                                                                                                            
    __name__ = 'user'                                                                                                          
                                                                                                                               
    def __init__(self, parent, request):                                                                                       
        self.__parent__ = parent                                                                                               
        self.request = request                                                                                                 
                                                                                                                               
    def __getitem__(self, key):                                                                                                
        db = get_dbgate(self.request)                                                                                          
        if not user_exists(db, key):                                                                                           
            raise KeyError()                                                                                                   
        return Username(key, parent=self)                                                                                      
                                                                                                                               
                                                                                                                               
class Username(object):                                                                                                        
    def __init__(self, name, parent):                                                                                          
        self.username = name                                                                                                   
        self.__name__ = name                                                                                                   
        self.__parent__ = parent                                                                                               
        self.__acl__ = [ (Allow, Authenticated, '%_view', username),                                                           
                         (Deny, Everyone, ALL_PERMISSIONS)                                                                     
                        ]