src/main/java/com/workplacesystems/utilsj/collections/TransactionalBidiTreeMap.java
private Node<K,V> leastValidNode(final Node<K,V> node, final int index, final String thread_id) {
        Node<K,V> lval = node;

        while (lval != null && !validNode(lval, thread_id)) {
            lval = nextSmaller(lval, index);
        }
        return lval;
    }
private Node<K,V> leastValidNode(final Node<K,V> node, final int index, final String thread_id) {
        Node<K,V> lval = node;

        while (lval != null && !validNode(lval, thread_id)) {
            lval = nextSmaller(lval, index);
        }
        return lval;
    }
find the least valid node from a given node. very useful for starting
a sorting iterator ...

@param node the node from which we will start searching
@param index KEY or VALUE

@return the smallest valid node, from the specified node, in the
specified mapping