def to_dict(self):
        """Return state as a dictionary.

        Result can be used to serialize the instance and reconstitute
        it later using :meth:`from_dict`.

        :rtype: dict
        """
        session = self._get_session()
        snapshot = self._get_snapshot()
        return {
            "session_id": session._session_id,
            "transaction_id": snapshot._transaction_id,
        }