new_contents: from django.contrib.auth.backends import ModelBackend
  from .models import BaseAccount, UserProfile
  
  
  
  class CustomAuthBackend(ModelBackend):
  
      def authenticate(self, request, username=None, password=None, **kwargs):
          if username is None:
              username = kwargs.get(UserModel.USERNAME_FIELD)
          try:
              user = UserModel._default_manager.get_by_natural_key(username)
          except UserModel.DoesNotExist:
              # Run the default password hasher once to reduce the timing
              # difference between an existing and a non-existing user (#20760).
              UserModel().set_password(password)
          else:
              if user.check_password(password) and self.user_can_authenticate(user):
                  return user
  
subject: Fix some bugs