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

    def candidates():
        if ('MRJOB_CONF' in os.environ):
            (yield expand_path(os.environ['MRJOB_CONF']))
        (yield expand_path(os.path.join('~', '.mrjob.conf')))
        (yield '/etc/mrjob.conf')
    for path in candidates():
        log.debug(('Looking    for    configs    in    %s' % path))
        if os.path.exists(path):
            log.info(('Using    configs    in    %s' % path))
            return path
    else:
        log.info('No    configs    found.
   falling    back    on    auto-configuration')
        return None

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

def find_mrjob_conf():