code: def _start_cluster(self) -> str:
      ray_rdd = self.sc.range(
          0, self.num_ray_nodes, numSlices=self.num_ray_nodes
      )
      from bigdl.dllib.nncontext import ZooContext
  
      if ZooContext.barrier_mode:
          print("Launching Ray on cluster with Spark barrier mode")
          # The first ip would be used to launch ray master.
          process_infos = (
              ray_rdd.barrier()
              .mapPartitions(
                  self.ray_service.gen_ray_start(self.cluster_ips[0])
              )
              .collect()
          )
      else:
          print("Launching Ray on cluster without Spark barrier mode")
          master_process_infos = ray_rdd.mapPartitionsWithIndex(
              self.ray_service.gen_ray_master_start()
          ).collect()
          master_process_infos = [
              process for process in master_process_infos if process
          ]
          invalidInputError(
              len(master_process_infos) == 1,
              "There should be only one ray master launched,"
              " but got {}".format(len(master_process_infos)),
          )
          master_process_info = master_process_infos[0]
          redis_address = master_process_info.master_addr
          raylet_process_infos = ray_rdd.mapPartitions(
              self.ray_service.gen_raylet_start(redis_address)
          ).collect()
          raylet_process_infos = [
              process for process in raylet_process_infos if process
          ]
          invalidInputError(
              len(raylet_process_infos) == self.num_ray_nodes - 1,
              "There should be {} raylets launched across the cluster, but got"
              " {}".format(
                  self.num_ray_nodes - 1, len(raylet_process_infos)
              ),
          )
          process_infos = master_process_infos + raylet_process_infos
  
      self.ray_processesMonitor = ProcessMonitor(
          process_infos,
          self.sc,
          ray_rdd,  # type: ignore
          self,
          verbose=self.verbose,
      )
      return self.ray_processesMonitor.master.master_addr
  
imports: import os
  import re
  import subprocess
  import time
  import uuid
  import random
  import warnings
  import tempfile
  import filelock
  import multiprocessing
  from packaging import version
  from bigdl.orca.ray.process import session_execute, ProcessMonitor
  from bigdl.orca.ray.utils import is_local
  from bigdl.orca.ray.utils import resource_to_bytes
  from bigdl.orca.ray.utils import get_parent_pid
  from bigdl.dllib.utils.log4Error import invalidInputError
  from typing import TYPE_CHECKING
  from typing import Any, Dict, Optional, List
label_desc: Use image node_id 12 for calling the RayOnSparkContext obj's underlying member method code with example usage: obj._start_cluster() and returns: self