def _validate_function(self, name, val):
        try:
            assert hasattr(val, "__call__")
        except AssertionError:
            raise Exception(name % "Invalid value for %s!  Must be a function.")
dataset/ETHPy150Open kxxoling/PTable/prettytable/prettytable.py/PrettyTable._validate_function/swapped operands of `%`