message: Implement required properties for TPU Strategy
  These properties are necessary for the strategy to work with
  `tf.estimator.train_and_evaluate`.
diff: @@ -307,6 +307,22 @@ class TPUStrategy(one_device_strategy.OneDeviceStrategy):
  def num_towers_per_host(self):
  return self._tpu_metadata.num_of_cores_per_host
  + @property
  + def between_graph(self):
  + return False
  +
  + @property
  + def should_init(self):
  + return True
  +
  + @property
  + def should_checkpoint(self):
  + return True
  +
  + @property
  + def should_save_summary(self):
  + return True
  +
  def get_host_cpu_device(self, host_id):
  if self._tpu_cluster_resolver.get_master() in ('', 'local'):
  return '/replica:0/task:0/device:CPU:0'
  @@ -324,4 +340,3 @@ class TPUStrategy(one_device_strategy.OneDeviceStrategy):
  cluster_spec = self._tpu_cluster_resolver.cluster_spec()
  if cluster_spec:
  session_config.cluster_def.CopyFrom(cluster_spec.as_cluster_def())
  -
  