code: def retrieve_metadata_server(metadata_key):
      
      url = METADATA_URL + metadata_key
  
      try:
          response = requests.get(url, headers=METADATA_HEADERS)
  
          if response.status_code == requests.codes.ok:
              return response.text
  
      except requests.exceptions.RequestException:
          # Ignore the exception, connection failed means the attribute does not
          # exist in the metadata server.
          pass
  
      return None
docs: Retrieve the metadata key in the metadata server.
  
      See: https://cloud.google.com/compute/docs/storing-retrieving-metadata
  
      :type metadata_key: str
      :param metadata_key: Key of the metadata which will form the url. You can
                           also supply query parameters after the metadata key.
                           e.g. "tags?alt=json"
  
      :rtype: str
      :returns: The value of the metadata key returned by the metadata server.