code: public static Predicate<RequestHandler> basePackage(final String basePackage) {
      return input -> declaringClass(input).map(handlerPackage(basePackage)).orElse(true);
    }
docs: Predicate that matches RequestHandler with given base package name for the class of the handler method.
  This predicate includes all request handlers matching the provided basePackage
  
  @param basePackage - base package of the classes
  @return this