    from umetrics import *
    from ribbonabc import RibbonAddInABC
    from tkinter import Tk, messagebox

    class AddInCommand(RibbonAddInABC):

        def on_command(Self) :
            root=Tk()
            root.withdraw()
            messagebox.showinfo(title= 'Hello', message= 'Hello World!')
            root.destroy()

        def get_button_name(Self):
            return 'Hello World!'
    group_order = [AddInCommand]