check and handle threat time out

def check_threat_timeout(self):
        '''check and handle threat time out'''
        for id in self.threat_vehicles.keys():
            if self.threat_vehicles[id].update_time == 0:
                self.threat_vehicles[id].update_time = self.get_time()
            dt = self.get_time() - self.threat_vehicles[id].update_time
            if dt > self.ADSB_settings.timeout:
                # if the threat has timed out...
                del self.threat_vehicles[id]  # remove the threat from the dict
                for mp in self.module_matching('map*'):
                    # remove the threat from the map
                    mp.map.remove_object(id)
                    mp.map.remove_object(id+":circle")
                # we've modified the dict we're iterating over, so
                # we'll get any more timed-out threats next time we're
                # called:
                return