*/
  public static <V1 extends @Nullable Object, V2 extends @Nullable Object>
      Combiner2<V1, V2> whenAllSucceed(ClosingFuture<V1> future1, ClosingFuture<V2> future2) {
    return new Combiner2<>(future1, future2);
  }

  /**
   * Starts specifying how to combine three {@link ClosingFuture}s into a single pipeline, assuming

    /*
     * Futures should be collected even if combiner never runs. This is kind of a silly test, since
     * the combiner is almost certain to hold its own reference to the futures, and a real app would
     * hold a reference to the executor and thus to the combiner. What we really care about is that
     * the futures are released once the combiner is done running. But we happen to provide this
     * earlier cleanup at the moment, so we're testing it.

    /*
     * Futures should be collected even if combiner never runs. This is kind of a silly test, since
     * the combiner is almost certain to hold its own reference to the futures, and a real app would
     * hold a reference to the executor and thus to the combiner. What we really care about is that
     * the futures are released once the combiner is done running. But we happen to provide this
     * earlier cleanup at the moment, so we're testing it.