code: func (s *fsStore) Save(listRef reference.Reference, manifest reference.Reference, image types.ImageManifest) error {
  	if err := s.createManifestListDirectory(listRef.String()); err != nil {
  		return err
  	}
  	filename := manifestToFilename(s.root, listRef.String(), manifest.String())
  	bytes, err := json.Marshal(image)
  	if err != nil {
  		return err
  	}
  	return ioutil.WriteFile(filename, bytes, 0644)
  }
docs: // Save a manifest as part of a local manifest list