/** Accepts a {@link ValueAndCloser} for the last step in a {@link ClosingFuture} pipeline. */
    void accept(ValueAndCloser<V> valueAndCloser);
  }

  /**
   * Starts a {@link ClosingFuture} pipeline by submitting a callable block to an executor.
   *
   * @throws java.util.concurrent.RejectedExecutionException if the task cannot be scheduled for
   *     execution
   */