@JaeHwanChoi the model writer will zip a given model to store it. Underneath there has to be a model that the package that you used can read(KNIME ML to Python - #2 by mlauber71 ). If you want to use it with Jupyter notebooks this has to work in both environments.
You could try and store a model just as pickel and use knime as interface for some python models. Here are examples from several versions of knime and python:
There are other frameworks you could use. Knime started to generically support Sklearn for certain models:
If you want to interact between knime and python maybe the H2O.ai framework is for you. You can interchange models via MOJO files.
You might derive further inspiration from this collection: