The example in the spec relies on the existence of a "parser" that returns buffers that are full valid segments. Most of the code is not included.
A much more simple example (with all the code included) will help developers to better understand the API and use it.
We could make the code sample format agnostic by not using a specific media type. However, I don't think this is what you're asking for. I think you're asking for the code for the functions not included but in a format agnostic way. As Aaron says, applications will not be able to ignore the format.
Resolving NEEDSINFO. Please provide the example you're asking for and we can review adding it to the spec or into a separate primer document.