code: func ReadBundleRevision(ctx context.Context, store storage.Store, txn storage.Transaction) (string, error) {
  
  	value, err := store.Read(ctx, txn, revisionPath)
  	if err != nil {
  		return "", err
  	}
  
  	str, ok := value.(string)
  	if !ok {
  		return "", fmt.Errorf("corrupt manifest revision")
  	}
  
  	return str, nil
  }
docs: // ReadBundleRevision returns the revision in the currently activated
  // bundle. If there is no activated bundle, ths function will return
  // storage NotFound error.