reactor-core/src/main/java/reactor/core/publisher/Mono.java
public final <P> P as(Function<? super Mono<T>, P> transformer) {
		return transformer.apply(this);
	}
public final <P> P as(Function<? super Mono<T>, P> transformer) {
		return transformer.apply(this);
	}
Transform this {@link Mono} into a target type.

<blockquote><pre>
{@code mono.as(Flux::from).subscribe() }
</pre></blockquote>

@param transformer the {@link Function} to immediately map this {@link Mono}
into a target type
@param <P> the returned instance type

@return the {@link Mono} transformed to an instance of P
@see #compose for a bounded conversion to {@link Publisher}