A good way to turn up examples using the introspected bindings offered by pygobject 3 (in contrast to the "old" static bindings offered by pygobject 2 and pygtk) is to use "gi.repository" as a search keyword. For example, searching for "gi.repository gst" quickly leads to a simple media player and the examples listed in the Novacut porting guide, amongst other goodies.
On documentation, best to follow the C API reference and/or consult the relevant .gir files. API references for other languages able to use introspected binding are generally not yet available, although tools to create them from the intermediate .gir files created by gobject-introspection's g-ir-scanner are being worked on.