code: public static ServiceRegistrarFactory load(final Path plugin,
                                               final ClassLoader environment,
                                               final ClassLoader parent)
        throws ServiceRegistrarLoadingException {
      return load("plugin jar file: " + plugin, pluginClassLoader(plugin, environment, parent));
    }
docs: Load a {@link ServiceRegistrarFactory} from a plugin jar file with a specified parent class
  loader and a list of exposed classes.
  
  @param plugin      The plugin jar file to load.
  @param environment The class loader to use for providing plugin interface dependencies.
  @param parent      The parent class loader to assign to the class loader of the jar.
  
  @return A {@link ServiceRegistrarFactory}, null if none could be found.
  
  @throws ServiceRegistrarLoadingException if loading failed.