    def _backend_logout_cleanup(self, name):
        """Default backend logout actions

        Send a log message, clear some cookies, increment the logout counter.
        """
        self.log.info("User logged out: %s", name)
        self.clear_login_cookie()
        self.statsd.incr('logout')
Default backend logout actions

Send a log message, clear some cookies, increment the logout counter.
jupyterhub/handlers/login.py