Uninstall the package with:

pip uninstall pgnhelper

The dependent libararies installed by pgnhelper are not uninstalled automatically. You have to uninstall it manually.

Uninstall other libraries:

pip uninstall chess
pip uninstall pandas
pip uninstall pretty-html-table
pip uninstall pytest


Do not uninstall the other libraries if you still need it specially if you install pgnhelper globally or not using virtual environment.