[prasoonds]

Hey, that's a fair question. I've responded to another question about why fork here: https://news.ycombinator.com/item?id=40857807

In short, for now, yes might have been able to implement this functionality as an extension (though there are several other changes that we've made to core Jupyter behavior as well). But our roadmap calls for much more sweeping changes to the code execution model itself and that simply cannot be an extension.