public function isLazy($key= '') {
        $lazy = false;
        if (empty($key)) {
            $lazy = (count($this->_lazy) > 0);
        } else {
            $key = $this->getField($key, true);
            if ($key !== false) {
                $lazy = in_array($key, $this->_lazy);
            }
        }
        return $lazy;
    }