protected function getRequest($method, $text = '', $source = '', $target = '')
    {
        $request = self::API_URL . '/' . $method . '?' . http_build_query(
            [
                'key' => $this->key,
                'source' => $source,
                'target' => $target,
                'q' => Html::encode($text),
            ]
        );

        return $request;
    }