Method whereHas

src/main/java/fieldbox/boxes/Box.java:194–197

(Dict.Prop<T> find, Function<Box, Collection<Box>> direction)

		return breadthFirst(direction).map(x -> x.properties.get(find))
			.filter(x -> x != null);
	}

	@HiddenInAutocomplete
	public <T> Stream<Box> whereHas(Dict.Prop<T> find, Function<Box, Collection<Box>> direction) {
		return breadthFirst(direction).filter(x -> x.properties.has(find));
	}