*/
  public static <
          V1 extends @Nullable Object, V2 extends @Nullable Object, V3 extends @Nullable Object>
      Combiner3<V1, V2, V3> whenAllSucceed(
          ClosingFuture<V1> future1, ClosingFuture<V2> future2, ClosingFuture<V3> future3) {
    return new Combiner3<>(future1, future2, future3);
  }

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

        Callable<C> combiner, Executor executor) {
      return new CombinedFuture<>(futures, allMustSucceed, executor, combiner);
    }

    /**
     * Creates the {@link ListenableFuture} which will return the result of running {@code combiner}
     * when all Futures complete. {@code combiner} will run using {@code executor}.
     *

    }

    /*
     * While the current implementation returns `this`, that's not something we mean to guarantee.
     * Anyway, the purpose of this method is to implement a BinaryOperator combiner for a Collector,
     * so its return value will get used naturally.
     */
    @SuppressWarnings("CanIgnoreReturnValueSuggester")
    Builder<K, V> combine(ImmutableSortedMap.Builder<K, V> other) {