code: def authenticate(self, token_value):
          
          try:
              backend_path, user_id = token_value.split(':', 1)
          except (ValueError, AttributeError):
              return False
          backend = auth.load_backend(backend_path)
          return bool(backend.get_user(user_id))
docs: Check that the password is valid.
  
          This allows for revoking of a user's preview rights by changing the
          valid passwords.