public function get_response_file_url(stored_file $file) {
        return file_encode_url(new moodle_url('/pluginfile.php'), '/' . implode('/', array(
                $file->get_contextid(),
                $file->get_component(),
                $file->get_filearea(),
                $this->usageid,
                $this->slot,
                $file->get_itemid())) .
                $file->get_filepath() . $file->get_filename(), true);
    }