public static <T> Stream<? extends T> walk(
            T first,
            UnaryOperator<T> traverser) {
        
        requireNonNulls(first, traverser);
        
        return walk(
            first, 
            traverser, 
            WalkingOrder.FORWARD, 
            Stream.builder()
        ).build();
    }
The walking order of the tree.
runtime-parent/runtime-config/src/main/java/com/speedment/runtime/config/internal/util/Trees.java