Hi @JaeHwanChoi,
The model writer writes objects in a KNIME specific data format meant to be read by Model Reader nodes. The python object reader / writer nodes were created to allow writing / reading of data in a format that can be understood by external python processes.
Take a look at this workflow for a workaround if you can’t use these nodes yet:
Python + KNIME expert @mlauber71 explains there how to read + write data inside python scripting nodes.
best,
Gabriel