default Stream<T> stream() {
		return breadthFirstStream();
	}
Return a stream that traverses the subtree rooted at {@code this} node in
breadth-first order. The first node returned by the stream is
{@code this} node.

@see #breadthFirstStream
@return a stream for traversing the tree in breadth-first order
jenetics.ext/src/main/java/io/jenetics/ext/util/Tree.java