public function download_buttons() {
        global $OUTPUT;

        if ($this->is_downloadable() && !$this->is_downloading()) {
            return $OUTPUT->download_dataformat_selector(get_string('downloadas', 'table'),
                    $this->baseurl->out_omit_querystring(), 'download', $this->baseurl->params());
        } else {
            return '';
        }
    }