snippet for my experiment presentation app. Why can't I create an instance within the build(self)?

main.py

from kivy.app import App
from kivy.uix.widget import Widget
from kivy.uix.label import Label
from kivy.graphics import Color, Ellipse, Line
from kivy.uix.boxlayout import BoxLayout
from kivy.core.window import Window
from kivy.interactive import InteractiveLauncher

framePoints = [150, 250, 750, 250, 750, 600, 150, 600, 150, 250]
CIRCLEPOSITIONS = ([200,300],[350,300],[500,300],[650,300],[200,400],[350,400],[500,400],[650,400],[200,500],[350,500],[500,500],[650,500])
CIRCLESIZE = 80

RED = (0.3,0.3,0.3)
BLUE = (.6, .8, .6)
WHITE = (1,1,1)


class Circles:

	def __init__(self, posx, posy, color):
			self.x = posx
			self.y = posy
			self.col = color
			
			
class Configuration:

	def __init__(self, nred = 6, nblue = 6):
			self.nred = nred
			self.nblue = nblue
			self.circles = []
			self.setupConf()
						
	def setupConf(self):
	
			circlePosz = list(CIRCLEPOSITIONS)
			
			for i in range(0,self.nred):
				coord = circlePosz.pop(0)
				self.circles.append(Circles(coord[0],coord[1],RED))
			
			for i in range(0,self.nblue):
				coord = circlePosz.pop(0)
				self.circles.append(Circles(coord[0],coord[1],BLUE))
	 		
	 		


class DisplayWidget(Widget):

  			
    def __init__(self, frame, circles, **kwargs):
        super(DisplayWidget, self).__init__(**kwargs)
#        Window.clearcolor = (0.1, 0.1, 0.1, 1.)


        with self.canvas:
        

                Color(*WHITE)
                Line(points=frame, width=2.5)           
                                                    
                for circle in setup.circles:            
                    Color(*circle.col)
                    d = CIRCLESIZE
                    Ellipse(pos=(circle.x , circle.y), size=(d, d))

##  here works
setup = Configuration(4,8)
        

class TiktokApp(App):

    def build(self):		

## here it makes it crash
#		setup = Configuration(4,8)


        layout = BoxLayout(orientation='vertical')
        display = DisplayWidget(framePoints, setup.circles)
        text = Label(text='Les circles sont TICK rouge')
        layout.add_widget(display)
        layout.add_widget(text)
        
        
               
        return layout

    def build_config(self, config):
        config.setdefaults('graphics', {
            'width': '1280',
            'height': '1024'
        })



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