protected function _stringifyNullBoolParams($apiparams)
  {
    foreach ($apiparams as $key => $value) {
      if (! is_scalar($value)) {
        // no need to try replacing arrays
        continue;
      }
      if (is_null($value)) {
        $apiparams[$key] = 'null';
      } elseif (is_bool($value)) {
        $apiparams[$key] = $value ? 'true' : 'false';
      }
    }

    return $apiparams;
  }