public function getNested($keyString, $default = null, $separator = '.')
    {
        $keys = explode($separator, $keyString);
        $data = $this->array;
        foreach ($keys as $key) {
            if(!is_array($data) or !array_key_exists($key, $data)) {
                return $default;
            }
            $data = $data[$key];
        }
        return $data;
    }