code: def main():
      parser = argparse.ArgumentParser(
          description="Launch a distributed job"
      )
      parser.add_argument(
          "-n",
          "--num-workers",
          required=True,
          type=int,
          help="number of worker nodes to be launched",
      )
      parser.add_argument(
          "-s",
          "--num-servers",
          type=int,
          help="number of server nodes to be launched, \
                          in default it is equal to NUM_WORKERS",
      )
      parser.add_argument(
          "-H",
          "--hostfile",
          type=str,
          help="the hostfile of slave machines which will run \
                          the job. Required for ssh and mpi launcher",
      )
      parser.add_argument(
          "--sync-dst-dir",
          type=str,
          help="if specificed, it will sync the current \
                          directory into slave machines's SYNC_DST_DIR if ssh \
                          launcher is used",
      )
      parser.add_argument(
          "--launcher",
          type=str,
          default="ssh",
          choices=["local", "ssh", "mpi", "sge", "yarn"],
          help="the launcher to use",
      )
      parser.add_argument(
          "--env-server",
          action="append",
          default=[],
          help="Given a pair of environment_variable:value, sets this value of \
                          environment variable for the server processes. This overrides values of \
                          those environment variable on the machine where this script is run from. \
                          Example OMP_NUM_THREADS:3",
      )
      parser.add_argument(
          "--env-worker",
          action="append",
          default=[],
          help="Given a pair of environment_variable:value, sets this value of \
                          environment variable for the worker processes. This overrides values of \
                          those environment variable on the machine where this script is run from. \
                          Example OMP_NUM_THREADS:3",
      )
      parser.add_argument(
          "--env",
          action="append",
          default=[],
          help="given a environment variable, passes their \
                          values from current system to all workers and servers. \
                          Not necessary when launcher is local as in that case \
                          all environment variables which are set are copied.",
      )
      parser.add_argument(
          "--p3",
          action="store_true",
          default=False,
          help="Use P3 distributed training",
      )
      parser.add_argument(
          "command", nargs="+", help="command for launching the program"
      )
      args, unknown = parser.parse_known_args()
      args.command += unknown
      if args.num_servers is None:
          args.num_servers = args.num_workers
      if args.p3:
          args.command = [
              "DMLC_PS_VAN_TYPE=p3 DMLC_PS_WATER_MARK=10"
          ] + args.command
  
      args = dmlc_opts(args)
  
      if args.host_file is None or args.host_file == "None":
          if args.cluster == "yarn":
              from dmlc_tracker import yarn
  
              yarn.submit(args)
          elif args.cluster == "local":
              from dmlc_tracker import local
  
              local.submit(args)
          elif args.cluster == "sge":
              from dmlc_tracker import sge
  
              sge.submit(args)
          else:
              raise RuntimeError(
                  f"Unknown submission cluster type {args.cluster}"
              )
      else:
          if args.cluster == "ssh":
              from dmlc_tracker import ssh
  
              ssh.submit(args)
          elif args.cluster == "mpi":
              from dmlc_tracker import mpi
  
              mpi.submit(args)
          else:
              raise RuntimeError(
                  f"Unknown submission cluster type {args.cluster}"
              )
  
imports: import argparse
  import os, sys
  import signal
  import logging
label_desc: Use image node_id 2 for calling a global function with example usage: main() without return types