@Mary_lea as I have mentioned. Your Python nodes have a data port (the small black triangle) configured but in the code there is no line that would create this data.
Such an output would look like this assuming df is a pandas dataframe (you might want to check the links provided above)
# bring the dataframe back to KNIME
knio.output_tables[0] = knio.Table.from_pandas(df)
If you do not want any output you can remove this port. Then you would have to take care about the output yourself.
You can read more about how the Python integration works here:
https://docs.knime.com/latest/python_installation_guide/#_introduction