code: def device_add(self, mountpoint, *device):
          
          if len(device) == 0:
              return
  
          args = {
              'mountpoint': mountpoint,
              'devices': device,
          }
  
          self._device_chk.check(args)
  
          self._client.sync('btrfs.device_add', args)
docs: Add one or more devices to btrfs filesystem mounted under `mountpoint`
  
          :param mountpoint: mount point of the btrfs system
          :param devices: one ore more devices to add
          :return: