human
I wrote the below code

    import mysensors.mysensors as mysensors
    version = config[DOMAIN].get(CONF_VERSION)
    persistence = config[DOMAIN].get(CONF_PERSISTENCE)
    def setup_gateway(device, persistence_file, baud_rate, tcp_port, in_prefix, out_prefix):
        'Return    gateway    after    setup    of    the    gateway.'
        if (device == MQTT_COMPONENT):
            if (not setup_component(hass, MQTT_COMPONENT, config)):
                return
            mqtt = get_component(MQTT_COMPONENT)
            retain = config[DOMAIN].get(CONF_RETAIN)
            def pub_callback(topic, payload, qos, retain):
                'Call    MQTT    publish    function.'
                mqtt.publish(hass, topic, payload, qos, retain)
            def sub_callback(topic, callback, qos):
                'Call    MQTT    subscribe    function.'
                mqtt.subscribe(hass, topic, callback, qos)
            gateway = mysensors.MQTTGateway(pub_callback, sub_callback, event_callback=None, persistence=persistence, persistence_file=persistence_file, protocol_version=version, in_prefix=in_prefix, out_prefix=out_prefix, retain=retain)
        else:
            try:
                is_serial_port(device)
                gateway = mysensors.SerialGateway(device, event_callback=None, persistence=persistence, persistence_file=persistence_file, protocol_version=version, baud=baud_rate)
            except vol.Invalid:
                try:
                    socket.getaddrinfo(device, None)
                    gateway = mysensors.TCPGateway(device, event_callback=None, persistence=persistence, persistence_file=persistence_file, protocol_version=version, port=tcp_port)
                except OSError:
                    return
        gateway.metric = hass.config.units.is_metric
        optimistic = config[DOMAIN].get(CONF_OPTIMISTIC)
        gateway = GatewayWrapper(gateway, optimistic, device)
        gateway.event_callback = gateway.callback_factory()
        def gw_start(event):
            'Trigger    to    start    of    the    gateway ...

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

def setup(hass, config):