Display a modal dialog box built from the classic (non-themed) Tk widgets and wait for the user to press one of its buttons. The options, given through cnf or as keyword arguments, are all required: title (the window title), text (the message), bitmap (the name of a bitmap icon, such as DIALOG_ICON), default (the index of the default button) and strings (the sequence of button labels). After construction, the num attribute holds the index of the button the user pressed.