class_docstr: tracker for rabit
docstr: get a ring connection used to recover local data
code: def get_ring(
      self, tree_map: _TreeMap, parent_map: Dict[int, int]
  ) -> _RingMap:
      """
      get a ring connection used to recover local data
      """
      assert parent_map[0] == -1
      rlst = self.find_share_ring(tree_map, parent_map, 0)
      assert len(rlst) == len(tree_map)
      ring_map: _RingMap = {}
      n_workers = len(tree_map)
      for r in range(n_workers):
          rprev = (r + n_workers - 1) % n_workers
          rnext = (r + 1) % n_workers
          ring_map[rlst[r]] = (rlst[rprev], rlst[rnext])
      return ring_map
  
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 7 for calling the RabitTracker obj's underlying member method code with example usage: obj.get_ring(tree_map, parent_map) and returns: ring_map