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

    conf = config.get(DOMAIN, {})
    cache = {}
    def service_handler(call):
        'Execute    a    shell    command    service.'
        cmd = conf[call.service]
        if (cmd in cache):
            (prog, args, args_compiled) = cache[cmd]
        elif ('    ' not in cmd):
            prog = cmd
            args = None
            args_compiled = None
            cache[cmd] = (prog, args, args_compiled)
        else:
            (prog, args) = cmd.split('    ', 1)
            args_compiled = template.Template(args, hass)
            cache[cmd] = (prog, args, args_compiled)
        if args_compiled:
            try:
                rendered_args = args_compiled.render(call.data)
            except TemplateError as ex:
                _LOGGER.exception('Error    rendering    command    template:    %s', ex)
                return
        else:
            rendered_args = None
        if (rendered_args == args):
            shell = True
        else:
            cmd = ([prog] + shlex.split(rendered_args))
            shell = False
        try:
            subprocess.call(cmd, shell=shell, stdout=subprocess.DEVNULL, stderr=subprocess.DEVNULL)
        except subprocess.SubprocessError:
            _LOGGER.exception('Error    running    command:    %s', cmd)
    for name in conf.keys():
        hass.services.register(DOMAIN, name, service_handler)
    return True

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

def setup(hass, config):