nbextensions in jupyter from sagemath

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Hello to everyone,

I am trying to install nbextensions for jupyter. I always run jupyter from sage with sage -n jupyter. I just upgraded (builr) to sage 9.1, then did sage -pip install jupyter_contrib_nbextensions. I got no error for that installation, but then when I launched sage -n jupyter I was expecting to see that extra tab for the extensions. It is not there, though.

Running on a unbutu18.04 machine.

Thanks! JC