code: public static <S> List<Class<? extends S>> load(Class<S> service) {
          return load(service, null);
      }
docs: Loads the classes of the providers of a service.
  
  @param service a service type.
  @return a list of classes implementing the given service type, using
  the current thread's context class loader.
  
  @throws ServiceConfigurationError if something goes wrong with loading
  a service provider's class.