code: func (s *IdentityService) DeleteUserLoginAttempts(user string) error {
  	if user == "" {
  		return trace.BadParameter("missing username")
  	}
  	startKey := backend.Key(webPrefix, usersPrefix, user, attemptsPrefix)
  	err := s.DeleteRange(context.TODO(), startKey, backend.RangeEnd(startKey))
  	if err != nil {
  		return trace.Wrap(err)
  	}
  	return nil
  }
docs: // DeleteUserLoginAttempts removes all login attempts of a user. Should be
  // called after successful login.