How to import the ipynb file that is in a different folder

Assuming there is a function files I want to import: `project/helper_fun.ipynb`
My current working ipynb file is: `project/branch/work.py`
when I write `from ipynb.fs.defs.helper_fun import fun1` in my`work.p`, it says`there is no module called helper_fun`

So my question is how to import the ipynb functions that are in a different folder.