code: public static ServiceRegistrarFactory load(final Path plugin)
        throws ServiceRegistrarLoadingException {
      return load(plugin, CURRENT, extensionClassLoader(CURRENT));
    }
docs: Load a {@link ServiceRegistrarFactory} from a plugin jar file with a parent class loader that
  will not load classes from the jvm classpath. Any dependencies of the plugin must be included
  in the plugin jar.
  
  @param plugin The plugin jar file to load.
  
  @return A {@link ServiceRegistrarFactory}, null if none could be found.
  
  @throws ServiceRegistrarLoadingException if loading failed.