code: public static <T> TracedParallelBatch<T> of(Promise<T>... promises) {
      return new TracedParallelBatch<>(Arrays.asList(promises));
    }
docs: Create a {@link TracedParallelBatch} for list of {@link Promise}s.
  
  @param promises vararg containing a list of {@link Promise}s.
  @param <T> the type of value produced by each promise
  
  @return an instance of {@link TracedParallelBatch}.