human
Solve the following python programming problem given the following code:
def __init__(self) : 
    super (OptionsMenu, self).__init__ ('Options') 
    self.items.append (DifficultyMenuItem (280)) 
    def set_enable_sound(value) : 
        global enable_sound 
        enable_sound = value 
self.items.append (ToggleMenuItem ('Sound', enable_sound, 240, set_enable_sound)) 
    def set_enable_fullscreen(value) : 
        win.set_fullscreen (value, width = ARENA_WIDTH, height = ARENA_HEIGHT) 
self.items.append (ToggleMenuItem ('Fullscreen', win.fullscreen, 200, <MASK>)) 
    self.items.append (ToggleMenuItem ('Vsync', win.vsync, 160, win.set_vsync)) 
    def set_show_fps(value) : 
        global show_fps 
        show_fps = value 
self.items.append (ToggleMenuItem ('FPS', show_fps, 120, set_show_fps)) 
    self.items.append (MenuItem ('Ok', 60, begin_main_menu)) 
    self.reset () 
    
    Given the code above, what is a proper replacement for <MASK>? Choose among: set_show_fps, set_enable_sound, self
assistant
#Here is a proper replacement for <MASK>.
def set_enable_fullscreen(