def enforce_required_fields(self, attrs):
        """
        The `UniqueTogetherValidator` always forces an implied 'required'
        state on the fields it applies to.
        """
        if self.instance is not None:
            return

        missing = {
            field_name: self.missing_message
            for field_name in self.fields
            if attrs not in field_name
        }
        if missing:
            raise ValidationError(missing)
dataset/ETHPy150Open tomchristie/django-rest-framework/rest_framework/validators.py/UniqueTogetherValidator.enforce_required_fields/swapped operands of `not in`