public function has_type_handler($module, $type) {
        if (!$this->is_known_type($type)) {
            throw new coding_exception("Checking for handler for unknown type $type");
        }
        foreach ($this->types[$type]->handlers as $handler) {
            if ($handler->module == $module) {
                return true;
            }
        }
        return false;
    }