def test_add_already_added(self):
        prio_set_list = event._PrioritizedSetList()
        obj = object()
        prio_set_list.add(0, obj)

        with pytest.raises(ValueError) as excinfo:
            prio_set_list.add(0, obj)
        excinfo.match(r"has already been added")

        with pytest.raises(ValueError) as excinfo:
            prio_set_list.add(1, obj)
        excinfo.match(r"has already been added")
def select_backend(self, backend_id=None):
        """
        Selects the backend corresponding to backend_id.
        If backend_id is none, refreshes the current configuration panel.

        @param backend_id: the id of the backend to select
        """
        selection = self.get_selection()
        if backend_id in self.backendid_to_iter:
            backend_iter = self.backendid_to_iter[backend_id]
            if selection:
                selection.select_iter(backend_iter)
        else:
            if self._get_selected_path():
                # We just reselect the currently selected entry
                self.on_select_row()
            else:
                # If nothing is selected, we select the first entry
                if selection:
                    selection.select_path("0")
        self.dialog.on_backend_selected(self.get_selected_backend_id())