ipynb is also in the ipython org and on pypi, and probably works, but hasn’t had a ton of development in a while. Probably doesn’t have filtering.
importnb (disclaimer: contributor) is a third package, and works fairly well. An interesting thing it does is actually uses an appropriately-updated line cache, so some surprising tools like debuggers actually “work” with it… but you’re stepping over JSON. It provides no capability to filter out content, though this has been requested several times.