Ishar, the dbutils.notebook.run() function is used to execute another notebook in a different session on the same cluster. Since the child notebook has a different session the variables, functions, parameters, classes, etc. are not available in the parent notebook.

If you wish to import a function from another notebook I would recommend using the %run functionality as that would execute the child notebook in the same session as the parent notebook.

To achieve your goal please use %run.

Additionally, if you are using python I would also look into our Python Import functionality that is available in Repos.