traceback

 Traceback (most recent call last):
   File "main.py", line 68, in <module>
     MyApp().run()
   File "/usr/lib/python3/dist-packages/kivy/app.py", line 855, in run
     runTouchApp()
   File "/usr/lib/python3/dist-packages/kivy/base.py", line 502, in runTouchApp
     EventLoop.window.mainloop()
   File "/usr/lib/python3/dist-packages/kivy/core/window/window_sdl2.py", line 724, in mainloop
     self._mainloop()
   File "/usr/lib/python3/dist-packages/kivy/core/window/window_sdl2.py", line 459, in _mainloop
     EventLoop.idle()
   File "/usr/lib/python3/dist-packages/kivy/base.py", line 340, in idle
     self.dispatch_input()
   File "/usr/lib/python3/dist-packages/kivy/base.py", line 325, in dispatch_input
     post_dispatch_input(*pop(0))
   File "/usr/lib/python3/dist-packages/kivy/base.py", line 231, in post_dispatch_input
     listener.dispatch('on_motion', etype, me)
   File "kivy/_event.pyx", line 707, in kivy._event.EventDispatcher.dispatch
   File "/usr/lib/python3/dist-packages/kivy/core/window/__init__.py", line 1360, in on_motion
     self.dispatch('on_touch_down', me)
   File "kivy/_event.pyx", line 707, in kivy._event.EventDispatcher.dispatch
   File "/usr/lib/python3/dist-packages/kivy/core/window/__init__.py", line 1376, in on_touch_down
     if w.dispatch('on_touch_down', touch):
   File "kivy/_event.pyx", line 707, in kivy._event.EventDispatcher.dispatch
   File "/usr/lib/python3/dist-packages/kivy/uix/widget.py", line 460, in on_touch_down
     if child.dispatch('on_touch_down', touch):
   File "kivy/_event.pyx", line 707, in kivy._event.EventDispatcher.dispatch
   File "/usr/lib/python3/dist-packages/kivy/uix/relativelayout.py", line 288, in on_touch_down
     ret = super(RelativeLayout, self).on_touch_down(touch)
   File "/usr/lib/python3/dist-packages/kivy/uix/widget.py", line 460, in on_touch_down
     if child.dispatch('on_touch_down', touch):
   File "kivy/_event.pyx", line 707, in kivy._event.EventDispatcher.dispatch
   File "<string>", line 6, in on_touch_down
 TypeError: super(type, obj): obj must be an instance or subtype of type