# Write a Python program to Stack and StackSwitcher in GTK+ 3 import gi# Since a system can have multiple versions# of GTK + installed, we want to make # sure that we are importing GTK + 3.gi.require_version("Gtk", "3.0")from gi.repository import Gtk    class StackWindow(Gtk.Window):    def __init__(self):        Gtk.Window.__init__(self, title ="Geeks for Geeks")        self.set_border_width(10)          # Creating a box vertically oriented with a space of 100 pixel.        vbox = Gtk.Box(orientation = Gtk.Orientation.VERTICAL, spacing = 100)        self.add(vbox)          # Creating stack, transition type and transition duration.        stack = Gtk.Stack()        stack.set_transition_type(Gtk.StackTransitionType.SLIDE_LEFT_RIGHT)        stack.set_transition_duration(1000)          # Creating the check button.        checkbutton = Gtk.CheckButton("Yes")        stack.add_titled(checkbutton, "check", "Check Button")          # Creating label .        label = Gtk.Label()        label.set_markup("<big>Hello World</big>")        stack.add_titled(label, "label", "Label")          # Implementation of stack switcher.        stack_switcher = Gtk.StackSwitcher()        stack_switcher.set_stack(stack)        vbox.pack_start(stack_switcher, True, True, 0)        vbox.pack_start(stack, True, True, 0)    win = StackWindow()win.connect("destroy", Gtk.main_quit)win.show_all()Gtk.main()