@staticmethod
def activate_scene_relay(scene_id, relay_ports=()):
    """Activate the stored relay states for the given scene.

        :param    int                scene_id:       Scene id 0..9
        :param    list(RelayPort)    relay_ports:    Relay ports to activate
                                                     as list
        :return:  The PCK command (without address header) as text
        :rtype:   str
        """
    if scene_id < 0 or scene_id > 9:
        raise ValueError('Wrong scene_id.')
    if not relay_ports:
        raise ValueError('relay_port list is empty.')
    relays_mask = ['0'] * 8
    for port in relay_ports:
        relays_mask[port.value] = '1'
    return 'SZA0{:03d}{:s}'.format(scene_id, ''.join(relays_mask))
