human
Solve the following python programming problem given the following code:
def install_signal_handlers(self) : 
    ' Handle events like Ctrl-C from the command line. ' 
    self.graceful_stop = False 
    def request_shutdown_now() : 
        self.shutdown_now () 
def request_shutdown_graceful() : 
        if self.graceful_stop : 
            request_shutdown_now () 
else : 
            self.graceful_stop = True 
            self.shutdown_graceful () 
gevent.signal (signal.SIGINT, <MASK>) 
    gevent.signal (signal.SIGTERM, request_shutdown_now) 
    
    Given the code above, what is a proper replacement for <MASK>? Choose among: request_shutdown_now, self
assistant
#Here is a proper replacement for <MASK>.
def request_shutdown_graceful(