def index(self):
        """Get the index of the day of the week.

        Returns
        -------
        IntegerValue
            The index of the day of the week. Ibis follows pandas conventions,
            where **Monday = 0 and Sunday = 6**.
        """
        import ibis.expr.operations as ops

        return ops.DayOfWeekIndex(self.op().arg).to_expr()