code: def testInitializeNoArgumentsWithTPUEnvironmentVariableTPUConfig(
      self,
  ):
      os.environ["TPU_CONFIG"] = json.dumps(
          {
              "project": "test-project",
              "zone": "us-central1-c",
              "tpu_node_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 19 for calling the CloudTpuClientTest obj's underlying member method code with example usage: obj.testInitializeNoArgumentsWithTPUEnvironmentVariableTPUConfig() without return types