code: func applyDefaultImageTag(image string) (string, error) {
  	named, err := dockerref.ParseNormalizedNamed(image)
  	if err != nil {
  		return "", fmt.Errorf("couldn't parse image reference %q: %v", image, err)
  	}
  	_, isTagged := named.(dockerref.Tagged)
  	_, isDigested := named.(dockerref.Digested)
  	if !isTagged && !isDigested {
  		// we just concatenate the image name with the default tag here instead
  		// of using dockerref.WithTag(named, ...) because that would cause the
  		// image to be fully qualified as docker.io/$name if it's a short name
  		// (e.g. just busybox). We don't want that to happen to keep the CRI
  		// agnostic wrt image names and default hostnames.
  		image = image + ":" + parsers.DefaultImageTag
  	}
  	return image, nil
  }
docs: // applyDefaultImageTag parses a docker image string, if it doesn't contain any tag or digest,
  // a default tag will be applied.