/usr/lib/x86_64-linux-gnu/qt5/qml/org/kde/plasma/private/sessions/qmldir is in plasma-workspace 4:5.8.6-2.1+deb9u1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 | module org.kde.plasma.private.sessions
plugin sessionsprivateplugin
|