private function get_groups_all() {
        if (is_null($this->groups)) {
            // NOTE: Performance could be improved here. The system caches user groups
            // in $USER->groupmember[$courseid] => array of groupid=>groupid. Unfortunately this
            // structure does not include grouping information. It probably could be changed to
            // do so, without a significant performance hit on login, thus saving this one query
            // each request.
            $this->groups = groups_get_user_groups($this->course->id, $this->userid);
        }
        return $this->groups;
    }