code: protected String extractResponse(Response response) {
  		requireArgument(response != null, "HttpResponse object cannot be null.");
  
  		return doExtractResponse(response.getStatusLine().getStatusCode(), response.getEntity());
  	}
docs: Helper to process the response. <br><br>
  Throws IllegalArgumentException when the http status code is in the 400 range <br>
  Throws SystemException when the http status code is outsdie of the 200 and 400 range
  @param response ES response
  @return	Stringified response