code: func newFSMetadataStore(root string) (*fileMetadataStore, error) {
  	if err := os.MkdirAll(root, 0700); err != nil {
  		return nil, err
  	}
  	return &fileMetadataStore{
  		root: root,
  	}, nil
  }
docs: // newFSMetadataStore returns an instance of a metadata store
  // which is backed by files on disk using the provided root
  // as the root of metadata files.