public static function posTagReadable($seg_list, $options = array())
    {
        $defaults = array(
            'mode'=>'default'
        );

        $options = array_merge($defaults, $options);

        $new_seg_list = array();

        foreach ($seg_list as $seg) {
            $seg['tag_readable'] = self::$pos_tag_readable[$seg['tag']];
            array_push($new_seg_list, $seg);
        }

        return $new_seg_list;
    }