code: func NewStore(dir string, store *imagestore.Store) (*Store, error) {
  	// TODO(sgotti) backward compatibility with the current tree store paths. Needs a migration path to better paths.
  	ts := &Store{dir: filepath.Join(dir, "tree"), store: store}
  
  	ts.lockDir = filepath.Join(dir, "treestorelocks")
  	if err := os.MkdirAll(ts.lockDir, 0755); err != nil {
  		return nil, err
  	}
  	return ts, nil
  }
docs: // NewStore creates a Store for managing filesystem trees, including the dependency graph resolution of the underlying image layers.