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    def _serialize_data(self, doc):
        _doc = doc.copy()
        for key, value in _doc.items():
            if isinstance(value, datetime):
                doc[key] = value.isoformat()
            elif isinstance(value, (ObjectId, uuid.UUID)):
                doc[key] = str(value)
        return doc

this part could open hidden fields if it was directly changed by db.collection.update

proposal is to use _id and make call to DB and get full document and use _serialize_document always