code: def testGkeEnvironmentForPod(self):
      os.environ["KUBE_GOOGLE_CLOUD_TPU_ENDPOINTS"] = (
          "grpc://10.120.27.5:8470,"
          "grpc://10.120.27.6:8470,"
          "grpc://10.120.27.7:8470,"
          "grpc://10.120.27.8:8470"
      )
  
      self.assertIn("KUBE_GOOGLE_CLOUD_TPU_ENDPOINTS", os.environ)
      cluster_resolver = resolver.TPUClusterResolver()
      self.assertEqual(
          compat.as_bytes("grpc://10.120.27.5:8470"),
          compat.as_bytes(cluster_resolver.master()),
      )
      actual_cluster_spec = cluster_resolver.cluster_spec()
      expected_proto = """
      job {
        name: 'worker'
        tasks { key: 0 value: '10.120.27.5:8470' }
        tasks { key: 1 value: '10.120.27.6:8470' }
        tasks { key: 2 value: '10.120.27.7:8470' }
        tasks { key: 3 value: '10.120.27.8:8470' }
      }
      """
      self._verifyClusterSpecEquality(
          actual_cluster_spec, expected_proto
      )
  
      del os.environ["KUBE_GOOGLE_CLOUD_TPU_ENDPOINTS"]
  
imports: import os
  import six
  from six.moves.urllib.error import URLError
  from tensorflow.core.protobuf.tpu import topology_pb2
  from tensorflow.python.client import session
  from tensorflow.python.distribute.cluster_resolver.tpu import tpu_cluster_resolver
  from tensorflow.python.eager import context
  from tensorflow.python.framework import config
  from tensorflow.python.framework import errors
  from tensorflow.python.framework import test_util
  from tensorflow.python.platform import test
  from tensorflow.python.platform import tf_logging
  from tensorflow.python.training import server_lib
  from tensorflow.python.util import compat
label_desc: Use image node_id 21 for calling the TPUClusterResolverTest obj's underlying member method code with example usage: obj.testGkeEnvironmentForPod() without return types