def _validate_header_style(self, val):
        try:
            assert val in ("cap", "title", "upper", "lower", None)
        except AssertionError:
            raise Exception("Invalid header style, use cap, title, upper, lower or None!")
dataset/ETHPy150Open kxxoling/PTable/prettytable/prettytable.py/PrettyTable._validate_header_style/original