def form_prefix(self, day_n, slot_n):
        """Form prefix made up of day number and slot number.

        - day number 1-7 for Monday to Sunday
        - slot 1-2 typically morning and afternoon
        """
        return (day_n, slot_n) % "day%s_%s"
dataset/ETHPy150Open arteria/django-openinghours/openinghours/views_edit.py/OpeningHoursEditView.form_prefix/swapped operands of `%`