How to use the jupyterhub.orm.new_session_factory function in jupyterhub

def init_db(self):
        """Create the database connection"""
        self.log.debug("Connecting to db: %s", self.db_url)
        try:
            self.session_factory = orm.new_session_factory(
                self.db_url,
                reset=self.reset_db,
                echo=self.debug_db,
                **self.db_kwargs
            )
            # trigger constructing thread local db property
            _ = self.db
        except OperationalError as e:
            self.log.error("Failed to connect to db: %s", self.db_url)
            self.log.debug("Database error was:", exc_info=True)
            if self.db_url.startswith('sqlite:///'):
                self._check_db_path(self.db_url.split(':///', 1)[1])
            self.log.critical('\n'.join([
                "If you recently upgraded JupyterHub, try running",
                "    jupyterhub upgrade-db",
                "to upgrade your JupyterHub database schema",

if urlinfo.password:
            # avoid logging the database password
            urlinfo = urlinfo._replace(
                netloc='{}:[redacted]@{}:{}'.format(
                    urlinfo.username, urlinfo.hostname, urlinfo.port
                )
            )
            db_log_url = urlinfo.geturl()
        else:
            db_log_url = self.db_url
        self.log.debug("Connecting to db: %s", db_log_url)
        if self.upgrade_db:
            dbutil.upgrade_if_needed(self.db_url, log=self.log)

        try:
            self.session_factory = orm.new_session_factory(
                self.db_url, reset=self.reset_db, echo=self.debug_db, **self.db_kwargs
            )
            self.db = self.session_factory()
        except OperationalError as e:
            self.log.error("Failed to connect to db: %s", db_log_url)
            self.log.debug("Database error was:", exc_info=True)
            if self.db_url.startswith('sqlite:///'):
                self._check_db_path(self.db_url.split(':///', 1)[1])
            self.log.critical(
                '\n'.join(
                    [
                        "If you recently upgraded JupyterHub, try running",
                        "    jupyterhub upgrade-db",
                        "to upgrade your JupyterHub database schema",
                    ]
                )

def shell(args=None):
    """Start an IPython shell hooked up to the jupyerhub database"""
    from .app import JupyterHub

    hub = JupyterHub()
    hub.load_config_file(hub.config_file)
    db_url = hub.db_url
    db = orm.new_session_factory(db_url, **hub.db_kwargs)()
    ns = {'db': db, 'db_url': db_url, 'orm': orm}

    import IPython

    IPython.start_ipython(args, user_ns=ns)