code: func (l *VolumeList) Set(value string) error {
  	volumes := strings.Split(value, ";")
  	newVols := make([]VolumeSpec, len(volumes))
  	for i, v := range volumes {
  		spec, err := l.parseSpec(v)
  		if err != nil {
  			return err
  		}
  		newVols[i] = *spec
  	}
  	*l = append(*l, newVols...)
  	return nil
  }
docs: // Set implements the Set() function of pflags.Value interface.
  // This function parses the string that contains source:destination pair.
  // When the destination is not specified, the source get copied into current
  // working directory in container.