code: def testDistributedFunctionPendingNodesServerReplaced(self):
      with ops.device(self.device_local):
          x1 = array_ops.ones([2, 2])
  
      @def_function.function
      def worker_fn(i):
          with ops.device(self.device_t1):
              mul = math_ops.matmul(i, i)
          with ops.device(self.device_t2):
              add = mul + i
          return add - i
  
      worker_fn.get_concrete_function(x1)
  
      num_calls = 10
      self._coord = coordinator.Coordinator()
  
      def thread_fn(device, results):
          with self._coord.stop_on_exception():
              for i in range(num_calls):
                  with ops.device(device):
                      y = worker_fn(x1)
                  results[i] = y.numpy()
  
      def update_server_def_fn():
          with self._coord.stop_on_exception():
              for i in range(num_calls):
                  context.update_server_def(
                      server_def=(
                          self.server_def_s1_s2_s3
                          if i % 2 == 0
                          else self.server_def_s1_s2
                      )
                  )
  
      results = [None] * num_calls
      threads = []
      threads.append(
          threading.Thread(
              target=thread_fn, args=(self.device_t1, results)
          )
      )
      threads.append(threading.Thread(target=update_server_def_fn))
      for t in threads:
          t.start()
      self._coord.join(threads)
      for result in results:
          np.testing.assert_array_equal([[2, 2], [2, 2]], result)
  
imports: import os
  import threading
  from absl.testing import parameterized
  import numpy
  from tensorflow.core.distributed_runtime.preemption import gen_check_preemption_op
  from tensorflow.core.protobuf import cluster_pb2
  from tensorflow.core.protobuf import tensorflow_server_pb2
  from tensorflow.python import pywrap_tfe
  from tensorflow.python.eager import context
  from tensorflow.python.eager import def_function
  from tensorflow.python.eager import executor
  from tensorflow.python.framework import errors
  from tensorflow.python.framework import ops
  from tensorflow.python.framework import test_util
  from tensorflow.python.ops import array_ops
  from tensorflow.python.ops import math_ops
  from tensorflow.python.ops import variables
  from tensorflow.python.platform import test
  from tensorflow.python.training import coordinator
  from tensorflow.python.training import server_lib
label_desc: Use image node_id 19 for calling the DynamicClusterTest obj's underlying member method code with example usage: obj.testDistributedFunctionPendingNodesServerReplaced() and returns: unknown