docs: @SafeVarargs
  	protected static Set<String> sortedConcat(Iterable<String>... iterables) {
  		final Set<String> set = new TreeSet<>();
  		for (final Iterable<String> iterable : iterables) {
  			for (final String obj : iterable) {
  				set.add(obj);
  			}
  		}
  		return set;
  	}