public function apiQueryString($type)
    {
        // basic query
        $query = ['ngrestCallType' => $type];

        $fields = [];
        foreach ($this->model->primaryKey() as $n) {
            $fields[] = $n;
        }
        // see if we have fields for this type
        if (count($this->getFields($type)) > 0) {
            foreach ($this->getFields($type) as $field) {
                $fields[] = $field;
            }
        }
        // do we have extra fields to expand
        if (count($this->config->getPointerExtraFields($type)) > 0) {
            $query['expand'] = implode(',', $this->config->getPointerExtraFields($type));
        }
        
        array_unique($fields);
        $query['fields'] = implode(",", $fields);

        if (Yii::$app->request->get('pool')) {
            $query['pool'] = Yii::$app->request->get('pool');
        }

        // return url decoded string from http_build_query
        return http_build_query($query, '', '&');
    }