code: def _start_cluster(self):
      ray_rdd = self.sc.range(
          0, self.num_ray_nodes, numSlices=self.num_ray_nodes
      )
      from zoo 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
          ]
          assert (
              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
          ]
          assert (
              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, 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 zoo.ray.process import session_execute, ProcessMonitor
  from zoo.ray.utils import is_local
  from zoo.ray.utils import resource_to_bytes
  from zoo.ray.utils import get_parent_pid
label_desc: Use image node_id 11 for calling the RayContext obj's underlying member method code with example usage: obj._start_cluster() and returns: self