Run
!pip install ipynb
and then import the other notebook as
from ipynb.fs.full.<notebook_name> import *
or
from ipynb.fs.full.<notebook_name> import <function_name>
Make sure that all the notebooks are in the same directory.
Edit 1: You can see the official documentation here - https://ipynb.readthedocs.io/en/stable/
Also, if you would like to import only class & function definitions from a notebook (and not the top level statements), you can use ipynb.fs.defs
instead of ipynb.fs.full
. Full uppercase variable assignment will get evaluated as well.