Make example look more like the API it references.

index.bs

@@ -7459,13 +7459,15 @@ readable and writable streams represent the two ends of a longer pipeline, with
 web developer code insert [=transform streams=] into the middle of them.
 
 <div class="example" id="example-endpoint-pair-usage">
- Assuming we had a web-platform-provided interface `Transformer` that had `readable` and
- `writable` attributes, web developers would write code like so:
+ Assuming a web-platform-fired "transform" event with a `transformer` attribute that is a
+ `Transformer` interface with `readable` and `writable` attributes, web developers would
+ write code like so:
 
  <xmp highlight="js">
- async function handleTransformer({readable, writable}) {
+ addEventListener("transform", ({transformer}) => {
+   const {readable, writable} = transformer;
    await readable.pipeThrough(new TransformStream(...)).pipeTo(writable);
- }
+ });
  </xmp>
 </div>