def schedule_once(self, callback, timeout=0):
        if not callable(callback):
            raise ValueError('callback must be a callable, got %s' % callback)
        event = ClockEvent(
            self, False, callback, timeout, self._last_tick, _hash(callback),
            True)
        return event
Extracts the index number and returns.
dataset/ETHPy150Open kivy/kivy/kivy/clock.py/ClockBase.schedule_once--crossover with--dataset/ETHPy150Open openstack/neutron/neutron/tests/functional/scheduler/test_dhcp_agent_scheduler.py/TestAutoSchedule._extract_index