    def clear_state(self):
        """Clear any state that should be cleared when the single-user server stops.

        State that should be preserved across single-user server instances should not be cleared.

        Subclasses should call super, to ensure that state is properly cleared.
        """
        self.api_token = ''
Clear any state that should be cleared when the single-user server stops.

State that should be preserved across single-user server instances should not be cleared.

Subclasses should call super, to ensure that state is properly cleared.
jupyterhub/spawner.py