code: public static <T> void isNullOrEmpty(Set<T> set, String message) {
  
  		isTrue(set == null || set.size() == 0, message);
  	}
docs: Tests if set is null or empty
  
  @param set     must be null or empty
  @param message to return in exception
  @param <T>     object type
  @throws IllegalArgumentException if list != null or list.size() greater than 0