human
I wrote the below code

    if (_reactor is None):
        from twisted.internet import reactor as _reactor
    finished = main(_reactor, *argv)
    codes = [0]
    stopping = []
    _reactor.addSystemEventTrigger('before', 'shutdown', stopping.append, True)
    def stop(result, stopReactor):
        if stopReactor:
            try:
                _reactor.stop()
            except ReactorNotRunning:
                pass
        if isinstance(result, Failure):
            if (result.check(SystemExit) is not None):
                code = result.value.code
            else:
                log.err(result, 'main    function    encountered    error')
                code = 1
            codes[0] = code
    def cbFinish(result):
        if stopping:
            stop(result, False)
        else:
            _reactor.callWhenRunning(stop, result, True)
    finished.addBoth(cbFinish)
    _reactor.run()
    sys.exit(codes[0])

What's a good function header?

=====
Here's a good function header?
assistant
#Here's a good function header.

def react(main, argv=(), _reactor=None):