human
Here's a good function header given the following:
I wrote the below code

    (reactor, reactor_thread) = threaded_reactor()
    if (reactor is None):
        raise ImportError('twisted    is    not    available    or    could    not    be    imported')
    try:
        ((timeout is None) or (timeout + 0))
    except TypeError:
        raise TypeError("'timeout'    argument    must    be    a    number    or    None")
    def decorate(func):
        def wrapper(*args, **kargs):
            q = Queue()
            def callback(value):
                q.put(None)
            def errback(failure):
                try:
                    failure.raiseException()
                except:
                    q.put(sys.exc_info())
            def g():
                try:
                    d = func(*args, **kargs)
                    try:
                        d.addCallbacks(callback, errback)
                    except AttributeError:
                        raise TypeError('you    must    return    a    twisted    Deferred    from    your    test    case!')
                except:
                    q.put(sys.exc_info())
            reactor.callFromThread(g)
            try:
                error = q.get(timeout=timeout)
            except Empty:
                raise TimeExpired(('timeout    expired    before    end    of    test    (%f    s.)' % timeout))
            if (error is not None):
                (exc_type, exc_value, tb) = error
                raise exc_type, exc_value, tb
        wrapper = make_decorator(func)(wrapper)
        return wrapper
    return decorate

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

def deferred(timeout=None):