* the pipeline is cancelled.
   *
   * <p>All objects the pipeline has captured for closing will begin to be closed asynchronously
   * <b>after</b> the returned {@code Future} is done: the future completes before closing starts,
   * rather than once it has finished.
   *
   * <p>After calling this method, you may not call {@link
   * #finishToValueAndCloser(ValueAndCloserConsumer, Executor)}, this method, or any other