code: def _get_bucket_attribute(bucket,
                            query_param,
                            xml_response_tag,
                            retry_params=None,
                            _account_id=None):
    
    api = storage_api._get_storage_api(retry_params=retry_params,
                                       account_id=_account_id)
    common.validate_bucket_path(bucket)
    status, headers, content = api.get_bucket('%s?%s' % (bucket, query_param))
  
    errors.check_status(status, [200], bucket, resp_headers=headers, body=content)
  
    root = ET.fromstring(content)
    if root.tag == xml_response_tag and root.text:
      return root.text
    return None
docs: Helper method to request a bucket parameter and parse the response.
  
    Args:
      bucket: A Google Cloud Storage bucket of form '/bucket'.
      query_param: The query parameter to include in the get bucket request.
      xml_response_tag: The expected tag in the xml response.
      retry_params: An api_utils.RetryParams for this call to GCS. If None,
        the default one is used.
      _account_id: Internal-use only.
  
    Returns:
      The xml value as a string.  None if the returned xml does not match expected
      format.
  
    Raises:
      errors.AuthorizationError: if authorization failed.
      errors.NotFoundError: if the bucket does not exist.