def search(self, start_ts, end_ts):
        """Called to query Mongo for documents in a time range.
        """
        for meta_collection_name in self._meta_collections():
            meta_coll = self.meta_database[meta_collection_name]
            for ts_ns_doc in meta_coll.find(
                {"_ts": {"$lte": end_ts, "$gte": start_ts}}
            ):
                yield ts_ns_doc
Called to query Mongo for documents in a time range.