code: func (ts *tagStore) Untag(ctx context.Context, tag string) error {
  	tagPath, err := pathFor(manifestTagPathSpec{
  		name: ts.repository.Named().Name(),
  		tag:  tag,
  	})
  	if err != nil {
  		return err
  	}
  
  	if err := ts.blobStore.driver.Delete(ctx, tagPath); err != nil {
  		switch err.(type) {
  		case storagedriver.PathNotFoundError:
  			return nil // Untag is idempotent, we don't care if it didn't exist
  		default:
  			return err
  		}
  	}
  
  	return nil
  }
docs: // Untag removes the tag association