public function add($url, $parentID = 0, $extract = \false, $callbackUrl = '')
    {
        $data = [
            'url'            => $url,
            'save_parent_id' => $parentID,
            'extract'        => ($extract ? 'True' : 'False'),
            'callback_url'   => $callbackUrl
        ];

        return $this->post('transfers/add', $data, \false);
    }