'See twisted.internet.interfaces.IReactorCore.addSystemEventTrigger.'

def addSystemEventTrigger(self, _phase, _eventType, _f, *args, **kw):

    assert callable(_f), ('%s    is    not    callable' % _f)
    if (_eventType not in self._eventTriggers):
        self._eventTriggers[_eventType] = _ThreePhaseEvent()
    return (_eventType, self._eventTriggers[_eventType].addTrigger(_phase, _f, *args, **kw))
