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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_last_doc(self):
 """Get the most recently modified document from Elasticsearch. This method is used to help define a time window within which documents may be in conflict after a MongoDB rollback. """

        try:
            result = self.elastic.search(
                index=self.meta_index_name,
                body={
                    "query": {"match_all": {}},
                    "sort": [{"_ts": "desc"}],
                },
                size=1
            )["hits"]["hits"]
            for r in result:
                r['_source']['_id'] = r['_id']
                return r['_source']
        except es_exceptions.RequestError:
            # no documents so ES returns 400 because of undefined _ts mapping
            return None