code: def mock_service_client(self, tpu_map=None):
      if tpu_map is None:
          tpu_map = {}
  
      mock_locations = mock.MagicMock()
      mock_locations.nodes.return_value = MockNodeClass(tpu_map)
  
      mock_project = mock.MagicMock()
      mock_project.locations.return_value = mock_locations
  
      mock_client = mock.MagicMock()
      mock_client.projects.return_value = mock_project
      return mock_client
  
imports: import datetime
  import json
  import os
  import time
  import urllib
  from absl import flags
  from tensorflow.python.platform import test
  from tensorflow.python.tpu.client import client
label_desc: Use image node_id 4 for calling the CloudTpuClientTest obj's underlying member method code with example usage: obj.mock_service_client(tpu_map) and returns: mock_client