text: from django.contrib.auth import get_user_model
  from django.contrib.auth.backends import ModelBackend
  
  
  class EmailBackEnd(ModelBackend):
    def authenticate(self, username=None, password=None, **kwargs):
      UserModel = get_user_model()
      try:
        user = UserModel.objects.get(email=username)
      except UserModel.DoesNotExist:
        return None
      else:
        if user.check_password(password):
          return user
      return None
  