public function deleteRange($key, $length) {
        $badKeys = [];

        for ($i = $key; $i < $key + $length; $i++) {
            array_push($badKeys, $i);
        }

        $this->_datas = array_diff_key($this->_datas, array_flip($badKeys));
        $this->_datas = array_values($this->_datas);
    }