@Override
    public void abort(Throwable cause) {
        requireNonNull(cause, "cause");
        for (StreamMessage<? extends T> source : sources) {
            source.abort(cause);
        }
    }
Relay items in order from subsequent {@link StreamMessage}s as a single {@link StreamMessage} source.
core/src/main/java/com/linecorp/armeria/common/stream/ConcatArrayStreamMessage.java