code: def testInitializeNoArgumentsWithEnvironmentVariable(self):
      os.environ["TPU_NAME"] = "tpu_name"
      tpu_map = {
          "projects/test-project/locations/us-central1-c/nodes/tpu_name": {
              "ipAddress": "10.1.2.3",
              "port": "8470",
              "state": "READY",
              "health": "HEALTHY",
          }
      }
      c = client.Client(
          service=self.mock_service_client(tpu_map=tpu_map)
      )
      self.assertClientContains(c)
  
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 18 for calling the CloudTpuClientTest obj's underlying member method code with example usage: obj.testInitializeNoArgumentsWithEnvironmentVariable() without return types