reactor-core/src/main/java/reactor/core/publisher/Operators.java
@SuppressWarnings("unchecked")
	@Nullable
	public static <T> QueueSubscription<T> as(Subscription s) {
		if (s instanceof QueueSubscription) {
			return (QueueSubscription<T>) s;
		}
		return null;
	}
@SuppressWarnings("unchecked")
	@Nullable
	public static <T> QueueSubscription<T> as(Subscription s) {
		if (s instanceof QueueSubscription) {
			return (QueueSubscription<T>) s;
		}
		return null;
	}
Returns the subscription as QueueSubscription if possible or null.
@param <T> the value type of the QueueSubscription.
@param s the source subscription to try to convert.
@return the QueueSubscription instance or null