code: def _GetMetadataRequest(self, metadata_url, params=None, timeout=None):
      
      headers = {'Metadata-Flavor': 'Google'}
      params = urlparse.urlencode(params or {})
      url = '%s?%s' % (metadata_url, params)
      request = urlrequest.Request(url, headers=headers)
      request_opener = urlrequest.build_opener(urlrequest.ProxyHandler({}))
      timeout = timeout or self.timeout
      return request_opener.open(request, timeout=timeout*1.1)
docs: Performs a GET request with the metadata headers.
  
      Args:
        metadata_url: string, the URL to perform a GET request on.
        params: dictionary, the query parameters in the GET request.
        timeout: int, timeout in seconds for metadata requests.
  
      Returns:
        HTTP response from the GET request.
  
      Raises:
        urlerror.HTTPError: raises when the GET request fails.