在PyGTK中，显示PNG文件的简单方法是什么？

import gtk
import pygtk
pygtk.require(\'2.0\')

class Gui:

    def __init__(self):

        # Create an Image object for a PNG file.
        file_name = \"file.png\"
        pixbuf = gtk.gdk.pixbuf_new_from_file(file_name)
        pixmap, mask = pixbuf.render_pixmap_and_mask()
        image = gtk.Image()
        image.set_from_pixmap(pixmap, mask)

        # Create a window.
        window = gtk.Window()
        window.set_title(\"PNG file\")
        window.connect(\"destroy\", gtk.main_quit)

        # Show the PNG file in the window.
        window.add(image)
        window.show_all()

if __name__ == \"__main__\":
    Gui()
    gtk.main()