Challenge #2 of 2

Q: 

Ok, you've just created a layout and mapped it to the URL /foo. You also already have a route and controller for /foo.

When you go to /foo, you can see (in the web debug toolbar) that the layout did "resolve" for this page. And yet, you don't see your layout! All you see is the content that's printed in your Twig template. What might be wrong?