code: def test_parse_rendezvous_raises_error_if_value_is_empty(
      self,
  ) -> None:
      config_strs = [
          "b=dummy1,a,c=dummy2",
          "b=dummy1,c=dummy2,a",
          "b=dummy1,a=,c=dummy2",
          "  a ",
      ]
  
      for config_str in config_strs:
          with self.subTest(config_str=config_str):
              with self.assertRaisesRegex(
                  ValueError,
                  r"^The rendezvous configuration option 'a' must have a value specified.$",
              ):
                  _parse_rendezvous_config(config_str)
  
imports: import threading
  import time
  import socket
  from datetime import timedelta
  from typing import List
  from unittest import TestCase
  from unittest.mock import patch
  from torch.distributed.elastic.rendezvous.utils import _PeriodicTimer, _delay, _matches_machine_hostname, _parse_rendezvous_config, _try_parse_port, parse_rendezvous_endpoint
label_desc: Use image node_id 4 for calling the UtilsTest obj's underlying member method code with example usage: obj.test_parse_rendezvous_raises_error_if_value_is_empty() without return types