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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 aggregations(self):
 """Get the single valued aggregations with respect to the previous time interval."""


        prev_month_start = get_prev_month(self.end, self.query.interval_)
        self.query.since(prev_month_start)
        agg = super().aggregations()
        if agg is None:
            agg = 0  # None is because NaN in ES. Let's convert to 0
        return agg