code: func WithRollback(ctx context.Context, client *containerd.Client, c *containers.Container) error {
  	prev, err := previous(ctx, client, c)
  	if err != nil {
  		return err
  	}
  	ss := client.SnapshotService(c.Snapshotter)
  	sInfo, err := ss.Stat(ctx, prev.Key)
  	if err != nil {
  		return err
  	}
  	snapshotImage, ok := sInfo.Labels[imageLabel]
  	if !ok {
  		return fmt.Errorf("snapshot %s does not have a service image label", prev.Key)
  	}
  	if snapshotImage == "" {
  		return fmt.Errorf("snapshot %s has an empty service image label", prev.Key)
  	}
  	c.Image = snapshotImage
  	c.SnapshotKey = prev.Key
  	return nil
  }
docs: // WithRollback rolls back to the previous container's revision