public TypeSet interfaces() {
      return new InterfaceSet(this);
    }

    /** Returns the types that are classes. */
    public TypeSet classes() {
      return new ClassSet();
    }

    @Override
    protected Set<TypeToken<? super T>> delegate() {
      ImmutableSet<TypeToken<? super T>> filteredTypes = types;
      if (filteredTypes == null) {