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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 _fix_review_dates(self, item):
 """Convert dates so ES detect them"""


        for date_field in ['timestamp', 'createdOn', 'lastUpdated']:
            if date_field in item.keys():
                date_ts = item[date_field]
                item[date_field] = unixtime_to_datetime(date_ts).isoformat()

        if 'patchSets' in item.keys():
            for patch in item['patchSets']:
                pdate_ts = patch['createdOn']
                patch['createdOn'] = unixtime_to_datetime(pdate_ts).isoformat()

                if 'approvals' in patch:
                    for approval in patch['approvals']:
                        adate_ts = approval['grantedOn']
                        approval['grantedOn'] = unixtime_to_datetime(adate_ts).isoformat()

        if 'comments' in item.keys():
            for comment in item['comments']:
                cdate_ts = comment['timestamp']
                comment['timestamp'] = unixtime_to_datetime(cdate_ts).isoformat()