code: private static void checkPreconditions(final Set<Object> possibleValues) {
  		if( possibleValues == null ) {
  			throw new NullPointerException("possibleValues Set should not be null");
  		} else if( possibleValues.isEmpty() ) {
  			throw new IllegalArgumentException("possibleValues Set should not be empty");
  		}
  	}
docs: Checks the preconditions for creating a new IsIncludedIn processor with a Set of Objects.
  
  @param possibleValues
  the Set of possible values
  @throws NullPointerException
  if possibleValues is null
  @throws IllegalArgumentException
  if possibleValues is empty