code: func validateDatastoreFolder(folder *object.Folder) (*object.Folder, error) {
  	ft, err := FindType(folder)
  	if err != nil {
  		return nil, err
  	}
  	if ft != VSphereFolderTypeDatastore {
  		return nil, fmt.Errorf("%q is not a datastore folder", folder.InventoryPath)
  	}
  	return folder, nil
  }
docs: // validateDatastoreFolder checks to make sure the folder is a datastore
  // folder, and returns it if it is, or an error if it isn't.