code: def testAddWorkerMidJob(self):
      cluster = data_service_test_base.TestCluster(num_workers=1)
      num_elements = 2 * multiprocessing.cpu_count() + 100
      ds = self.make_distributed_range_dataset(num_elements, cluster)
      iterator = iter(ds)
      results = []
      # Read halfway through the dataset.
      for _ in range(num_elements // 2):
          results.append(next(iterator).numpy())
  
      cluster.add_worker()
      # Wait for the new worker to register with the dispatcher.
      while cluster.num_registered_workers() < 2:
          time.sleep(10 / 1000)  # 10ms
  
      for elem in iterator:
          results.append(elem.numpy())
  
      self.assertCountEqual(2 * list(range(num_elements)), results)
  
imports: import multiprocessing
  import threading
  import time
  from absl.testing import parameterized
  from tensorflow.python.data.experimental.kernel_tests.service import test_base
  from tensorflow.python.data.experimental.ops import data_service_ops
  from tensorflow.python.data.kernel_tests import test_base
  from tensorflow.python.data.ops import dataset_ops
  from tensorflow.python.framework import combinations
  from tensorflow.python.framework import dtypes
  from tensorflow.python.ops import array_ops
  from tensorflow.python.platform import test
label_desc: Use image node_id 12 for calling the FaultToleranceTest obj's underlying member method code with example usage: obj.testAddWorkerMidJob() without return types