'Switch up in the window list'

def cmd_up(self):

    win = None
    if self._focused:
        win = self._nodes[self._focused].get_prev_window()
    if (not win):
        win = self._tree.get_last_window()
    if win:
        self.group.focus(win.window, False)
    self._focused = (win.window if win else None)
