Fig. 14.17 shows a buggy contains() method for the
LockFreeSkipList class. Give a scenario where this method returns a
wrong answer. Hint: the reason this method is wrong is that it takes
into account keys of nodes that have been removed.
```
boolean contains(T x) {
int bottomLevel = 0;
int key = x.hashCode();
Node<T> pred = head;
Node<T> curr = null;
for (int level = MAX_LEVEL; level >= bottomLevel; level--) {
curr = pred.next[level].getReference();
while (curr.key < key ) {
pred = curr;
curr = pred.next[level].getReference();
}
}
return curr.key == key;
}
```