def stack_window(new_win, parent_win):
    """Elevate the new window to the topmost level of the stack of windows.

    :param new_win: the new window to be stacked on top.
    :type new_win: `tkinter.Toplevel`
    :param parent_win: the parent window of new_win.
    :type parent_win: `tkinter.Toplevel`
    """
    new_win.lift(parent_win)
    parent_win.attributes('-topmost', False)
    new_win.attributes('-topmost', True)
    new_win.attributes('-topmost', False)
