code: def start(self):
      try:
          if not self._check_if_exist():
              self._create_service()
          self._wait_service_ready()
          return self._mars_endpoint
      except:  # noqa: E722
          self.stop()
          raise
  
imports: import logging
  import time
  import warnings
  import requests
  from ...session import new_session
  from .config import MarsSchedulerSpecConfig, MarsWorkerSpecConfig, MarsWebSpecConfig, MarsJobConfig
label_desc: Use image node_id 6 for calling the KubeDLCluster obj's underlying member method code with example usage: obj.start() and returns: self