[Python] Alterar tela pelo arquivo python em kivy

Preciso alterar a tela dentro do arquivo .py, não consigo fazer isso pelo .kv pois tenho que usar o ButtonBehavior e ele não funciona no .kv.

from kivy.app import App
from kivy.uix.boxlayout import BoxLayout
from kivy.uix.button import ButtonBehavior
from kivy.uix.image import Image, AsyncImage
from kivy.uix.screenmanager import ScreenManager, Screen

import json
import requests


class TelaInicio(Screen):
pass


class TelaLigas(Screen):
def on_enter(self, *args):
url = requests.get('http://127.0.0.1:8000/api/ligas')
res = json.loads(url.text)
for i in res:
self.ids.ligas.add_widget(ListaLigas(ligas=i['imagem']))


class TelaTorneios(Screen):
pass


class ListaLigas(BoxLayout, ButtonBehavior, Image):
def __init__(self, ligas, manager=None, **kwargs):
super(ListaLigas, self).__init__(**kwargs)
self.manager = manager
self.l = str(ligas)
self.add_widget(AsyncImage(source=self.l))

def on_press(self):
print('ok')
self.manager.troca_tela_torneios()


class Manager(ScreenManager):
def __init__(self, **kwargs):
super(Manager, self).__init__(**kwargs)
self.lista_ligas = ListaLigas(self)

def troca_tela_torneios(self):
self.current = 'tela_torneios'

def troca_tela_ligas(self):
self.current = 'tela_ligas'

def troca_tela_inicio(self):
self.current = 'tela_inicio'


class Main(App):
def build(self):
return Manager()


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


O erro:

File "/home/marcelo/PycharmProjects/EAnimaApp/main.py", line 36, in on_press self.manager.troca_tela_torneios() AttributeError: 'NoneType' object has no attribute 'troca_tela_torneios'
​

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