public function getLtiByRlid($resource_link_id)
    {
        foreach($this->lessons->modules as $mod) {
            if ( ! isset($mod->lti) ) continue;
            foreach($mod->lti as $lti ) {
                if ( $lti->resource_link_id == $resource_link_id) return $lti;
            }
        }
        return null;
    }