code: func cleanPath(s string) (string, error) {
  	s = strings.Trim(s, "/")
  	if strings.HasPrefix(s, ":") {
  		return "", fmt.Errorf("Path cannot be made up of just a tag: %q", s)
  	}
  	return s, nil
  }
docs: // cleanPath removes leading and trailing forward slashes
  // and makes sure that the path does not only contain a tag.