Python Glade : Connection between button and label

import gi
gi.require_version('Gtk', '3.0')
from gi.repository import Gtk

class Handler:
    def OnShowClick(self,button):
        x.builder.get_object("label1").show_all()
   
   
    def OnChangeClick(self,button):
        x.builder.get_object("label1").set_text("My name is khafi")
   
   
    def OnHideClick(self,button):
        x.builder.get_object("label1").hide_on_delete()
   
   
    def OnExitClick(self,button):
        x.builder.get_object("window1").destroy()
   


class Example:
    def __init__(self):
        self.builder = Gtk.Builder()
        self.builder.add_from_file("Khafi.glade")
        self.builder.connect_signals(Handler())
        window = self.builder.get_object("window1")
        window.show_all()
    def main(self):
        Gtk.main()
x = Example()
x.main()