private function is_renderable() {
        global $CFG;
        if (empty($CFG->enableportfolios)) {
            return false;
        }
        if (defined('PORTFOLIO_INTERNAL')) {
            // something somewhere has detected a risk of this being called during inside the preparation
            // eg forum_print_attachments
            return false;
        }
        if (empty($this->instances) || count($this->instances) == 0) {
            return false;
        }
        return true;
    }