default StreamMessageDuplicator<T> toDuplicator() {
        return toDuplicator(defaultSubscriberExecutor());
    }
Returns a new {@link StreamMessageDuplicator} that duplicates this {@link StreamMessage} into one or
more {@link StreamMessage}s, which publish the same elements.
Note that you cannot subscribe to this {@link StreamMessage} anymore after you call this method.
To subscribe, call {@link StreamMessageDuplicator#duplicate()} from the returned
{@link StreamMessageDuplicator}.
core/src/main/java/com/linecorp/armeria/common/stream/StreamMessage.java