code: def create_model_instance(self, data):
          
          return self.model(
              session_key=self._get_or_create_session_key(),
              session_data=self.encode(data),
              expire_date=self.get_expiry_date(),
          )
docs: Return a new instance of the session model object, which represents the
          current session state. Intended to be used for saving the session data
          to the database.
          :param data: