class_docstr: tracker for rabit
docstr: Strat the tracker, it will wait for `n_workers` to connect.
code: def start(self, n_workers: int) -> None:
      """Strat the tracker, it will wait for `n_workers` to connect."""
  
      def run() -> None:
          self.accept_workers(n_workers)
  
      self.thread = Thread(target=run, args=(), daemon=True)
      self.thread.start()
  
imports: import argparse
  import logging
  import socket
  import struct
  import sys
  from threading import Thread
  from typing import Dict, List, Optional, Set, Tuple, Union
label_desc: Use image node_id 11 for calling the RabitTracker obj's underlying member method code with example usage: obj.start(n_workers) without return types