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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 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()