@Override
    public long demand() {
        // Since the objects is drained as soon as it is requested, The demand will be zero in most cases.
        // But the demand could be one if a subscriber calls `subscription.request(n)` while receiving a object
        // via 'onNext(t)'
        return requested ? 1 : 0;
    }
Constructs a new {@link TwoElementFixedStreamMessage} for the given objects.
core/src/main/java/com/linecorp/armeria/internal/common/stream/TwoElementFixedStreamMessage.java