def add_ordering(self, *ordering):
        """
        Adds items from the 'ordering' sequence to the query's "order by"
        clause. These items are either field names (not column names) --
        possibly with a direction prefix ('-' or '?') -- or ordinals,
        corresponding to column positions in the 'select' list.

        If 'ordering' is empty, all ordering is cleared from the query.
        """
        errors = []
        for item in ordering:
            if not ORDER_PATTERN.match(item):
                errors.append(item)
        if errors:
            raise FieldError(errors % 'Invalid order_by arguments: %s')
        if ordering:
            self.order_by.extend(ordering)
        else:
            self.default_ordering = False
dataset/ETHPy150Open AppScale/appscale/AppServer/lib/django-1.5/django/db/models/sql/query.py/Query.add_ordering/swapped operands of `%`