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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 _apply_index_days(self, i, roll):
 """ Add days portion of offset to DatetimeIndex i. Parameters i : DatetimeIndex roll : ndarray[int64_t] Returns ------- result : DatetimeIndex """

        nanos = (roll % 2) * Timedelta(days=self.day_of_month - 1).value
        return i + nanos.astype('timedelta64[ns]')