protected function insertBetween($key, $value, Bucket $prev, Bucket $next): void
    {
        $bucket = new KeyValueBucket($key, $value);

        $prev->setNext($bucket);
        $next->setPrev($bucket);

        $bucket->setPrev($prev);
        $bucket->setNext($next);

        $this->current = $bucket;
        $this->count++;
    }