def METHOD_NAME(self, dropdown, _pspec, end):
    if end.subject and end.subject.opposite and end.subject.opposite.type:
        UML.recipes.set_navigability(
            end.subject.association,
            end.subject,
            self.NAVIGABILITY[dropdown.get_selected()],
        )
        # Call this again, or non-navigability will not be displayed
        self.item.update_ends()