Creates a marker output.

        :param list[int] asset_quantities: The asset quantity list.
        :param bytes metadata: The metadata contained in the output.
        :return: An object representing the marker output.
        :rtype: TransactionOutput

def _get_marker_output(self, asset_quantities, metadata):
        """
        Creates a marker output.

        :param list[int] asset_quantities: The asset quantity list.
        :param bytes metadata: The metadata contained in the output.
        :return: An object representing the marker output.
        :rtype: TransactionOutput
        """
        payload = openassets.protocol.MarkerOutput(asset_quantities, metadata).serialize_payload()
        script = openassets.protocol.MarkerOutput.build_script(payload)
        return bitcoin.core.CTxOut(0, script)