protected function getFormParams($parameters = array())
    {
        $formParams = $parameters;

        if (!array_key_exists('api_output', $formParams)) {
            $formParams['api_output'] = Api::DEFAULT_OUTPUT;
        }

        if (!array_key_exists('api_key', $formParams)) {
            $formParams['api_key'] = $this->apiKey;
        }

        return $formParams;
    }