langchain/callbacks/mlflow_callback.py/MlflowLogger/start_run
class MlflowLogger:    def start_run(self, name: str, tags: Dict[str, str]) -> None:
        """To start a new run, auto generates the random suffix for name"""
        if name.endswith("-%"):
            rname = "".join(random.choices(string.ascii_uppercase + string.digits, k=7))
            name = name.replace("%", rname)
        self.run = self.mlflow.MlflowClient().create_run(
            self.mlf_expid, run_name=name, tags=tags
        )