public void AddLast(CircularLinkedListNode <T> node)
 {
     VerifyBlankNode(node);
     if (first == null)
     {
         node.SelfReference(this);
         first = node;
     }
     else
     {
         node.InsertBetween(first.back, first, this);
     }
     count++;
     version++;
 }