code: func getStage1InterfaceVersion(cdir string) (int, error) {
  	b, err := ioutil.ReadFile(common.Stage1ManifestPath(cdir))
  	if err != nil {
  		return -1, errwrap.Wrap(errors.New("error reading pod manifest"), err)
  	}
  
  	s1m := schema.ImageManifest{}
  	if err := json.Unmarshal(b, &s1m); err != nil {
  		return -1, errwrap.Wrap(errors.New("error unmarshaling stage1 manifest"), err)
  	}
  
  	if iv, ok := s1m.Annotations.Get(interfaceVersion); ok {
  		v, err := strconv.Atoi(iv)
  		if err != nil {
  			return -1, errwrap.Wrap(errors.New("error parsing interface version"), err)
  		}
  		return v, nil
  	}
  
  	// "interface-version" annotation not found, assume version 1
  	return 1, nil
  }
docs: // getStage1InterfaceVersion retrieves the interface version from the stage1
  // manifest for a given pod