code: func (s *IdentityService) DeleteWebSession(user, sid string) error {
  	if user == "" {
  		return trace.BadParameter("missing username")
  	}
  	if sid == "" {
  		return trace.BadParameter("missing session id")
  	}
  	err := s.Delete(context.TODO(), backend.Key(webPrefix, usersPrefix, user, sessionsPrefix, sid))
  	return trace.Wrap(err)
  }
docs: // DeleteWebSession deletes web session from the storage