human
Solve the following python programming problem given the following code:
@ classmethod 
def reset_clipboard(cls) : 
    def _reset_clipboard() : 
        if (cls.cb is not None) : 
            sublime.set_clipboard (cls.cb) 
cls.cb = None 
        cls.thread = None 
cls.thread = threading.Timer (0.5, <MASK>) 
    cls.thread.start () 
    
    Given the code above, what is a proper replacement for <MASK>? Choose among: cls
assistant
#Here is a proper replacement for <MASK>.
def _reset_clipboard(