class Configuration implements Iterable<Map.Entry<String,String>>,
                                      Writable {

  private void overlay(Properties to, Properties from) {
    for (Entry<Object, Object> entry: from.entrySet()) {
      to.put(entry.getKey(), entry.getValue());
    }
  }

  public  Configuration();
  public  Configuration(boolean loadDefaults);
  @SuppressWarnings("unchecked") public  Configuration(Configuration other);

}