code: func (s *IdentityService) DeleteUsedTOTPToken(user string) error {
  	if user == "" {
  		return trace.BadParameter("missing user name")
  	}
  	return s.Delete(context.TODO(), backend.Key(webPrefix, usersPrefix, user, usedTOTPPrefix))
  }
docs: // DeleteUsedTOTPToken removes the used token from the backend. This should only
  // be used during tests.