public function restAfterKey($key)
    {
        $key = $this->getKey($key);

        if ( ! array_key_exists($key, $this->items))
        {
            throw new OffsetNotExistsException('Key: '. $key .' not exists');
        }

        $index = $this->keys()->flip()->get($key);

        return $this->restAfterIndex($index);
    }