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

    if ('env' in load):
        salt.utils.warn_until('Oxygen', "Parameter    'env'    has    been    detected    in    the    argument    list.        This    parameter    is    no    longer    used    and    has    been    replaced    by    'saltenv'    as    of    Salt    2016.11.0.        This    warning    will    be    removed    in    Salt    Oxygen.")
        load.pop('env')
    if (load['saltenv'] not in __opts__['file_roots']):
        return []
    list_cachedir = os.path.join(__opts__['cachedir'], 'file_lists', 'roots')
    if (not os.path.isdir(list_cachedir)):
        try:
            os.makedirs(list_cachedir)
        except os.error:
            log.critical('Unable    to    make    cachedir    {0}'.format(list_cachedir))
            return []
    list_cache = os.path.join(list_cachedir, '{0}.p'.format(load['saltenv']))
    w_lock = os.path.join(list_cachedir, '.{0}.w'.format(load['saltenv']))
    (cache_match, refresh_cache, save_cache) = salt.fileserver.check_file_list_cache(__opts__, form, list_cache, w_lock)
    if (cache_match is not None):
        return cache_match
    if refresh_cache:
        ret = {'files': set(), 'dirs': set(), 'empty_dirs': set(), 'links': {}}
        def _add_to(tgt, fs_root, parent_dir, items):
            '\n                                                Add    the    files    to    the    target    set\n                                                '
            def _translate_sep(path):
                '\n                                                                Translate    path    separators    for    Windows    masterless    minions\n                                                                '
                return (path.replace('\\', '/') if (os.path.sep == '\\') else path)
            for item in items:
                abs_path = os.path.join(parent_dir, item)
                log.trace('roots:    Processing    %s', abs_path)
                is_link = salt.utils.path.islink(abs_path)
                log.trace('roots:    %s    is    %sa   ...

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

def _file_lists(load, form):