*
   * @since 13.0
   */
  public class TypeSet extends ForwardingSet<TypeToken<? super T>> implements Serializable {

    @CheckForNull private transient ImmutableSet<TypeToken<? super T>> types;

    TypeSet() {}

    /** Returns the types that are interfaces implemented by this type. */
    public TypeSet interfaces() {
      return new InterfaceSet(this);
    }