def unget_byte(self):
        # this is a one trick pony...don't call it twice
        assert self._pos > 0
        self._pos -= 1
Raise an assertion if there's no parents to return.
dataset/ETHPy150Open denisenkom/pytds/pytds/tds.py/_TdsReader.unget_byte--crossover with--dataset/ETHPy150Open cidles/poio-api/src/poioapi/tests/test_data.py/TestDataStructureType.test_get_parents_of_type