code: func ValidateLabel(val string) (string, error) {
  	if strings.Count(val, "=") < 1 {
  		return "", fmt.Errorf("bad attribute format: %s", val)
  	}
  	return val, nil
  }
docs: // ValidateLabel validates that the specified string is a valid label, and returns it.
  // Labels are in the form on key=value.