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.
docstr: Return runtime version of the TPU.
code: def runtime_version(self):
      """Return runtime version of the TPU."""
  
      if not self._use_api:
          # Fallback on getting version directly from TPU.
          url = _VERSION_SWITCHER_ENDPOINT.format(
              self.network_endpoints()[0]["ipAddress"]
          )
          try:
              req = urllib.request.Request(url)
              resp = urllib.request.urlopen(req)
              version_details = json.loads(resp.read())
              return version_details.get("currentVersion")
          except urllib.error.HTTPError as e:
              status_code = e.code
              if status_code == 404:
                  return None
              else:
                  raise e
      return self._get_tpu_property("tensorflowVersion")
  
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 15 for calling the Client obj's underlying member method code with example usage: obj.runtime_version() and returns: self, version_details, None