Kivy: how to create a clock without a widget?

Question

I would like to use the clock from Kivy but I would like to do it without using a "Widget". When I run the program, it will open a black window of my widget "Top" (there is no .kv file), and I don't need it.

Maybe there is some other way to do it without Kivy, I need to call the function "game.update" at periodic time intervals. thank your for your help

from kivy.app import App
from kivy.uix.widget import Widget
from kivy.clock import Clock

class Node:

    def __init__(self):
        self.inTrans = 0
        self.outTrans = 0

    def update(self):
        print('   Node:', self.inTrans, self.outTrans)
        self.inTrans = self.outTrans


class REQ():

    def __init__(self):
        self.outTrans=0
        self.inTrans=0
        self.count = 0

    def update(self):
        self.count += 4
        print("  requestor update, count:", self.count)
        self.outTrans = self.count
        return self.outTrans

class RES():

    def __init__(self):
        self.outTrans=0
        self.inTrans=0

    def update(self, inT):
        print("  responder update input:", inT)
        return

class Top(Widget):

    def __init__(self):
        super(Top, self).__init__()
        print("START")
        self.frame =0
        self.requester = REQ()
        self.responder = RES()
        self.node0 = Node()


    def update(self, dt):
        self.frame += 1
        print("Frame:", self.frame)
        self.node0.outTrans = self.requester.update()
        self.responder.update(self.node0.inTrans)
        self.node0.update()

        return




class TopApp(App):

    def build(self):
        game = Top()
        Clock.schedule_interval(game.update, 1.0 )
        return game


if __name__ == '__main__':
    TopApp().run()