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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def get_builder_toplevel(self, builder):
 """Get the toplevel widget from a gtk.Builder file. The main view implementation first searches for the widget named as self.toplevel_name (which defaults to "main". If this is missing, or not a gtk.Window, the first toplevel window found in the gtk.Builder is used. """

        toplevel = builder.get_object(self.toplevel_name)
        if not gobject.type_is_a(toplevel, gtk.Window):
            toplevel = None
        if toplevel is None:
            toplevel = get_first_builder_window(builder)
        return toplevel