public function page($pageSize = 10, $currentPage = 0)
    {
        if ($pageSize === static::$pageAll) {
            return $this;
        }
        /* normalize $currentPage and $currentPage */
        if (!is_numeric($currentPage) || $currentPage < 0) {
            $currentPage = 0;
        }
        $currentPage = (int) $currentPage;
        if (!is_numeric($pageSize) || $pageSize < 1) {
            $pageSize = static::$defaultPageSize;
        }
        $pageSize = (int) $pageSize;
        return $this->limit($pageSize)->offset($pageSize * $currentPage);
    }