def _mapper(self, data):
        for item in data:
            if self.mapping:
                for k, v in self.mapping.items():
                    item['doc'][k] = item['doc'][v]
                    del item['doc'][v]
            # print(doc)
            yield item
mapping old key to new key
dataset/ETHPy150Open zhongbiaodev/py-mysql-elasticsearch-sync/es_sync/__init__.py/ElasticSync._mapper