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

    def callback(filehandle, msg):
        'Writing    to    file    and    flushing    result'
        msg = ('\n%s    [-]    %s' % (timeformat(), msg.strip()))
        filehandle.write(msg)
        filehandle.flush()
    def errback(failure):
        'Catching    errors    to    normal    log'
        log_trace()
    filehandle = _open_log_file(filename)
    if filehandle:
        deferToThread(callback, filehandle, msg).addErrback(errback)

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

def log_file(msg, filename='game.log'):