code: protected synchronized List<T> initialize(List<T> plugins) {
  
  		Assert.notNull(plugins, "Plugins must not be null!");
  
  		return plugins.stream() //
  				.filter(it -> it != null) //
  				.collect(Collectors.toList());
  	}
docs: Callback to initialize the plugin {@link List}. Will create a defensive copy of the {@link List} to potentially
  unwrap a {@link List} proxy. Will filter {@literal null} values from the source list as well.
  
  @param plugins must not be {@literal null}.
  @return