@Override
	public boolean hasNext() {
		final var peek = queue.peek();
		return peek != null && peek.hasNext();
	}
Create a new (<em>property</em>) breath-first iterator from the given
arguments.

@param object the root object of the model
@param dtor the extractor function which extracts the direct
       extractable properties
@param mapper mapper function for creating the source object for the
       next level from the extracted objects of type {@code T}
@param identity objects, returned by this function are used for identifying
       already visited source objects, for preventing infinite loops
jenetics.incubator/src/main/java/io/jenetics/incubator/beans/internal/BreathFirstIterator.java