I'm writing an application that needs to use an indicator. I've done this in the past using PyGTK and GTK2, using as reference this document: https://wiki.ubuntu.com/DesktopExperienceTeam/ApplicationIndicators#Python_version
However, that only works with PyGTK and GTK2. Things have changed since then, and I need to find some good documentation, a tutorial or a good example to learn how it works.
Also, one thing that the previously mentioned document doesn't describe at all, is how to add sub-menus to an indicator. I hope someone can shed some light on this, as well as how to integrate with category indicators if that's done using the same tool.