src/main/java/io/reactivex/Completable.java
@CheckReturnValue
    @SchedulerSupport(SchedulerSupport.NONE)
    public final <R> R as(@NonNull CompletableConverter<? extends R> converter) {
        return ObjectHelper.requireNonNull(converter, "converter is null").apply(this);
    }
@CheckReturnValue
    @SchedulerSupport(SchedulerSupport.NONE)
    public final <R> R as(@NonNull CompletableConverter<? extends R> converter) {
        return ObjectHelper.requireNonNull(converter, "converter is null").apply(this);
    }
Calls the specified converter function during assembly time and returns its resulting value.
<p>
<img width="640" height="751" src="https://raw.github.com/wiki/ReactiveX/RxJava/images/rx-operators/Completable.as.png" alt="">
<p>
This allows fluent conversion to any other type.
<dl>
<dt><b>Scheduler:</b></dt>
<dd>{@code as} does not operate by default on a particular {@link Scheduler}.</dd>
</dl>
<p>History: 2.1.7 - experimental
@param <R> the resulting object type
@param converter the function that receives the current Completable instance and returns a value
@return the converted value
@throws NullPointerException if converter is null
@since 2.2