'Add slave(s) to and existing zone (multi-room).
Zone must already exist and slaves array can not be empty.
:param slaves:slaves to add'

def add_zone_slave(self, slaves):

    if (not slaves):
        _LOGGER.warning('Unable    to    find    slaves    to    add')
    else:
        _LOGGER.info(('Adding    slaves    to    zone    with    master    ' + str(self.device.config.name)))
        self.device.add_zone_slave([slave.device for slave in slaves])
