langchain/callbacks/mlflow_callback.py/MlflowLogger/langchain_artifact
class MlflowLogger:    def langchain_artifact(self, chain: Any) -> None:
        with self.mlflow.start_run(
            run_id=self.run.info.run_id, experiment_id=self.mlf_expid
        ):
            self.mlflow.langchain.log_model(chain, "langchain-model")