code: func (opt *WeightdeviceOpt) Set(val string) error {
  	var value *blkiodev.WeightDevice
  	if opt.validator != nil {
  		v, err := opt.validator(val)
  		if err != nil {
  			return err
  		}
  		value = v
  	}
  	(opt.values) = append((opt.values), value)
  	return nil
  }
docs: // Set validates a WeightDevice and sets its name as a key in WeightdeviceOpt