class_docstr: Client for working with the Cloud TPU API.
  
  This client is intended to be used for resolving tpu name to ip addresses.
  
  It's recommended to use this library as a contextlib to utilize all
  functionality.
code: def _get_tpu_property(self, key):
      if self._use_api:
          metadata = self._fetch_cloud_tpu_metadata()
          return metadata.get(key)
  
      return None
  
imports: from concurrent import futures
  import datetime
  import json
  import logging
  import os
  import time
  import urllib
  from absl import flags
label_desc: Use image node_id 8 for calling the Client obj's underlying member method code with example usage: obj._get_tpu_property(key) and returns: None, metadata