My solution was to tell Python of that additional module import path by adding a snippet like this one to the notebook:

import os

import sys

module_path = os.path.abspath(os.path.join('..'))

if module_path not in sys.path:

  sys.path.append(module_path)

This allows you to import the desired function from the module hierarchy:

from project1.lib.module import function

# use the function normally

function(...)

Note that it is necessary to add empty __init__.py files to project1/ and lib/ folders if you don't have them already.

If you want to know more about functions in Python go through EncodingCompiler