def stop(self, devices):
        """Power-Off one or more running devices.
        """
        for device in devices:
            self.logger.info('Stopping: %s', device.id)
            try:
                device.power_off()
            except packet.baseapi.Error:
                raise PacketManagerException('Unable to stop instance "{}"'.format(device.id))
Power-Off one or more running devices.