[Python] Python - Login Code not working in Kivy

The following error is appearing when I try to run this code. I tried in both versions of Python (2 and 3):

Syntax Error: Invalid syntax
​

from Kivy.app import App
from Kivy.uix.label import Label
from kivy.uix.gridlayout import GridLayout
from kivy.uix.textinput import TextInput

class LoginScreen(GridLayout):
def __init__(self, **kwargs):
super(LoginScreen, self).__init__(**kwargs)
self.cols = 2
self.add_widget(Label(text="Username:"))
self.username = TextInput(multiline=False)
self.add_widget(self.username)

class SimpleKivy(App):
def build(sef):
return LoginScreen()

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