docs: public static void belongsTo(File directory, File parameter, String name) throws IllegalArgumentException {
  		String dirPath = directory.getAbsolutePath();
  		String filePath = parameter.getAbsolutePath();
  		if (!filePath.startsWith(dirPath)) {
  			throw new IllegalArgumentException(String.format("%s |%s| is outside directory |%s|.", name, filePath, dirPath));
  		}
  	}