code: def clear_uservars(self, user=None):
          
  
          if user is None:
              # All the users!
              self._session.reset_all()
          else:
              # Just this one.
              self._session.reset(user)
docs: Delete all variables about a user (or all users).
  
          :param str user: The user ID to clear variables for, or else clear all
              variables for all users if not provided.