generic treatment of intermediate extensions (nb.py, etc)
generic treatment of intermediate extensions (nb.py, etc)

mwouts/jupytext,mwouts/jupytext,mwouts/jupytext,mwouts/jupytext,mwouts/jupytext,mwouts/jupytext,mwouts/jupytext,mwouts/jupytext,mwouts/jupytext,mwouts/jupytext