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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 get_zeroth_quarter_idx(self, stacked_last_per_qtr):
 """ Filters for releases that are on or after each simulation date and determines the previous quarter by picking out the most recent release relative to each date in the index. Parameters stacked_last_per_qtr : pd.DataFrame A DataFrame with index of calendar dates, sid, and normalized quarters with each row being the latest estimate for the row's index values, sorted by event date. Returns ------- previous_releases_per_date_index : pd.MultiIndex An index of calendar dates, sid, and normalized quarters, for only the rows that have a previous event. """

        previous_releases_per_date = stacked_last_per_qtr.loc[
            stacked_last_per_qtr[EVENT_DATE_FIELD_NAME] <=
            stacked_last_per_qtr.index.get_level_values(SIMULATION_DATES)
        ].groupby(
            level=[SIMULATION_DATES, SID_FIELD_NAME],
            as_index=False,
            # Here we take advantage of the fact that `stacked_last_per_qtr` is
            # sorted by event date.
        ).nth(-1)
        return previous_releases_per_date.index