Can import a exists ipynb file

The `ipynb` is not a editable format. It doesn't like the markdown that what you see is what you get. when i create a new post with ipynb format. Actually my flow like this:

1. Open ipython notebook server and create a notebook named A.ipynb
2. edit it, add the contents of the I want to express 
3. use `nikola new_post -f ipynb` create one ipynb file  named B.ipynb
4. find the A.ipynb file and replace B.ipynb

I think i only need import a exists ipynb file directly when create a post is better.