docs: public static ExtensionComponentSet union(final Collection<? extends ExtensionComponentSet> base) {
          return new ExtensionComponentSet() {
              @Override
              public <T> Collection<ExtensionComponent<T>> find(Class<T> type) {
                  List<ExtensionComponent<T>> r = Lists.newArrayList();
                  for (ExtensionComponentSet d : base)
                      r.addAll(d.find(type));
                  return r;
              }
          };
      }