src/main/java/com/workplacesystems/utilsj/collections/TransactionalBidiTreeMap.java
private static <K,V> void makeBlack(final Node<K,V> node, final int index) {

        if (node != null) {
            node.setBlack(index);
        }
    }
private static <K,V> void makeBlack(final Node<K,V> node, final int index) {

        if (node != null) {
            node.setBlack(index);
        }
    }
force a node (if it exists) black

@param node the node (may be null) in question
@param index KEY or VALUE