code: def start_rabit_tracker(args):
      """Standalone function to start rabit tracker.
  
      Parameters
      ----------
      args: arguments to start the rabit tracker.
      """
      envs = {
          "DMLC_NUM_WORKER": args.num_workers,
          "DMLC_NUM_SERVER": args.num_servers,
      }
      rabit = RabitTracker(
          hostIP=get_host_ip(args.host_ip), nslave=args.num_workers
      )
      envs.update(rabit.slave_envs())
      rabit.start(args.num_workers)
      sys.stdout.write("DMLC_TRACKER_ENV_START\n")
      # simply write configuration to stdout
      for k, v in envs.items():
          sys.stdout.write("%s=%s\n" % (k, str(v)))
      sys.stdout.write("DMLC_TRACKER_ENV_END\n")
      sys.stdout.flush()
      rabit.join()
  
imports: from __future__ import absolute_import
  import os
  import sys
  import socket
  import struct
  import subprocess
  import argparse
  import time
  import logging
  from threading import Thread
label_desc: Use image node_id 5 for calling a global function with example usage: start_rabit_tracker(args) without return types