internal class Node<TKey, TValue>
    {
        private TKey _key;
        private TValue _value;
        private Node<TKey, TValue> _left;
        private Node<TKey, TValue> _right;
        private Node<TKey, TValue> _parent;

        public Node(TKey key, TValue value)
        {
            _key = key;
            _value = value;
        }
    }