def index(self) -> dict:
        """
        Return dict mapping content sequence numbers to schema keys.

        :return: dict mapping sequence numbers to schema keys
        """

        LOGGER.debug('SchemaCache.index >>>')

        rv = self._seq_no2schema_key
        LOGGER.debug('SchemaCache.index <<< %s', rv)
        return rv
Return dict mapping content sequence numbers to schema keys.

        :return: dict mapping sequence numbers to schema keys