/**
   * Starts specifying how to combine two {@link ClosingFuture}s into a single pipeline, assuming
   * they all succeed. If any fail, the resulting pipeline will fail.
   *
   * <p>Calling this method allows you to use lambdas or method references typed with the types of
   * the input {@link ClosingFuture}s.
   *
   * @throws IllegalStateException if a {@code ClosingFuture} has already been derived from any of