def validate(self):
        super(FamilyMembers, self).validate()
        if self.sex and 'mf' not in self.sex:
            raise ValidationError("FamilyMember.sex must be one of ['m', 'f']")

        if self.birth_year and self.sex == 'f':
            raise ValidationError("FamilyMember.birth_year is set, and 'a lady never tells'")
dataset/ETHPy150Open datastax/python-driver/example_mapper.py/FamilyMembers.validate/swapped operands of `not in`