}

    @SuppressWarnings("unchecked") // proxy for a generic class
    <V1, V2, U> AsyncClosingFunction2<V1, V2, U> waitFor(
        AsyncClosingFunction2<V1, V2, U> asyncClosingFunction2) {
      return waitFor(asyncClosingFunction2, AsyncClosingFunction2.class);
    }

    @SuppressWarnings("unchecked") // proxy for a generic class