pythonのrandom.randintの引数について

kivyで作ったスロットマシンのコードです。15,16行目の

python
1def change_value(self,dt):
2        self.value = random.randint(0,9)
3

の引数のdtはなぜ必要なのでしょうか。試しにdtを消して実行すると

`Traceback (most recent call last):
File "main.py", line 53, in <module>
SlotApp().run()
File "/Users/babayoshimichi/.pyenv/versions/3.6.5/lib/python3.6/site-packages/kivy/app.py", line 855, in run
runTouchApp()
File "/Users/babayoshimichi/.pyenv/versions/3.6.5/lib/python3.6/site-packages/kivy/base.py", line 504, in runTouc

hApp
EventLoop.window.mainloop()
File "/Users/babayoshimichi/.pyenv/versions/3.6.5/lib/python3.6/site-packages/kivy/core/window/window_sdl2.py", l
ine 747, in mainloop
self._mainloop()
File "/Users/babayoshimichi/.pyenv/versions/3.6.5/lib/python3.6/site-packages/kivy/core/window/window_sdl2.py", l
ine 479, in _mainloop
EventLoop.idle()
File "/Users/babayoshimichi/.pyenv/versions/3.6.5/lib/python3.6/site-packages/kivy/base.py", line 339, in idle
Clock.tick()
File "/Users/babayoshimichi/.pyenv/versions/3.6.5/lib/python3.6/site-packages/kivy/clock.py", line 591, in tick
self._process_events()
File "kivy/_clock.pyx", line 384, in kivy._clock.CyClockBase._process_events
File "kivy/_clock.pyx", line 414, in kivy._clock.CyClockBase._process_events
File "kivy/_clock.pyx", line 412, in kivy._clock.CyClockBase._process_events
File "kivy/_clock.pyx", line 167, in kivy._clock.ClockEvent.tick
TypeError: change_value() takes 1 positional argument but 2 were given`

というエラーが出ます。ご教示お願いいたします。

python
1from kivy.app import App
2from kivy.clock import Clock
3from kivy.properties import NumericProperty
4from kivy.uix.boxlayout import BoxLayout
5from kivy.uix.button import Button
6from kivy.uix.label import Label
7import random
8
9class SlotLabel(Label):
10    value = NumericProperty(0)
11    font_size = 48
12    evt = None
13    def on_value(self,*args):
14        self.text = str(self.value)
15    def change_value(self):
16        self.value = random.randint(0,9)
17
18class SlotButton(Button):
19    counter = 0
20    font_size = 28
21    def on_press(self):
22        upper_box = self.parent.children[1]
23        if self.counter == 0:
24            for lbl in upper_box.children:
25                lbl.evt = Clock.schedule_interval(lbl.change_value, 0.05)
26            self.text = 'Stop'
27        elif self.counter == 4:
28            for lbl in upper_box.children:
29                lbl.value = 0
30            self.text = 'Start'
31        else:
32            lbl = upper_box.children[3-self.counter]
33            lbl.evt.cancel()
34            if self.counter == 3:
35                self.text = 'Reset'
36        self.counter += 1
37        if self.counter == 5:
38            self.counter = 0
39
40class SlotApp(App):
41    def build(self):
42        root_box = BoxLayout(orientation='vertical')
43        upper_box = BoxLayout(size_hint_y=9)
44
45        upper_box.add_widget(SlotLabel(text='0'))
46        upper_box.add_widget(SlotLabel(text='0'))
47        upper_box.add_widget(SlotLabel(text='0'))
48
49        root_box.add_widget(upper_box)
50        root_box.add_widget(SlotButton(text='Start'))
51        return root_box
52
53SlotApp().run()