class_docstr: Use mlflow to implement ExpManager.
code: def _start_exp(
      self,
      *,
      experiment_id: Optional[Text] = None,
      experiment_name: Optional[Text] = None,
      recorder_id: Optional[Text] = None,
      recorder_name: Optional[Text] = None,
      resume: bool = False,
  ):
      # Create experiment
      if experiment_name is None:
          experiment_name = self._default_exp_name
      experiment, _ = self._get_or_create_exp(
          experiment_id=experiment_id, experiment_name=experiment_name
      )
      # Set up active experiment
      self.active_experiment = experiment
      # Start the experiment
      self.active_experiment.start(
          recorder_id=recorder_id,
          recorder_name=recorder_name,
          resume=resume,
      )
  
      return self.active_experiment
  
imports: from urllib.parse import urlparse
  import mlflow
  from filelock import FileLock
  from mlflow.exceptions import MlflowException, RESOURCE_ALREADY_EXISTS, ErrorCode
  from mlflow.entities import ViewType
  import os
  from typing import Optional, Text
  from .exp import MLflowExperiment, Experiment
  from ..config import C
  from .recorder import Recorder
  from ..log import get_module_logger
  from ..utils.exceptions import ExpAlreadyExistError
label_desc: Use image node_id 2 for calling the MLflowExpManager obj's underlying member method code with example usage: obj._start_exp() and returns: self