/**
* flatten nested SimpleReactStreams
*
* @param stream Stream to flatten
* @return flattened Stream
*/
static <U, R> SimpleReactStream<R> join(SimpleReactStream<SimpleReactStream<U>> stream) {
Queue queue = stream.getQueueFactory().build();
stream.then(it -> it.sync().then(queue::offer)).allOf(it -> queue.close());
return stream.fromStream(queue.stream(stream.getSubscription()));
}
