How does the reference counting work in the presence of reference cycles involving both the GTK side and the Python side, e.g. an event handler having a referen

How does the reference counting work in the presence of reference cycles involving both the GTK side and the Python side, e.g. an event handler having a reference to an object that has a reference to the object the handler is attached to? Do they get collected properly, like they would with pure Python objects, or would you have to break up the cycle?