pyside6-assistant is a tool that wraps Qt Assistant, the help viewer of Qt for use with the Qt help file format (see The Qt Help Framework).

The version of assistant shipped with Qt for Python does not contain any documentation.

You can build the Qt for Python documentation in the Qt help file format (see Building the documentation) and register it for use in Preferences dialog of pyside6-assistant (Edit/Preferences).

PySide6 Assistant Screenshot