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

        return ((node == null)
                ? true
                : node.isBlack(index));
    }
private static <K,V> boolean isBlack(final Node<K,V> node, final int index) {

        return ((node == null)
                ? true
                : node.isBlack(index));
    }
is the specified black red? if the node does not exist, sure,
it's black, thank you

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