code: func (d *Driver) getLayerChain(id string) ([]string, error) {
  	jPath := filepath.Join(d.dir(id), "layerchain.json")
  	content, err := ioutil.ReadFile(jPath)
  	if os.IsNotExist(err) {
  		return nil, nil
  	} else if err != nil {
  		return nil, fmt.Errorf("Unable to read layerchain file - %s", err)
  	}
  
  	var layerChain []string
  	err = json.Unmarshal(content, &layerChain)
  	if err != nil {
  		return nil, fmt.Errorf("Failed to unmarshall layerchain json - %s", err)
  	}
  
  	return layerChain, nil
  }
docs: // getLayerChain returns the layer chain information.