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

self.authenticator.normalize_username(name)
            for name in self.authenticator.whitelist
        ]
        self.authenticator.whitelist = set(whitelist)  # force normalization
        for username in whitelist:
            if not self.authenticator.validate_username(username):
                raise ValueError("username %r is not valid" % username)

        if not whitelist:
            self.log.info("Not using whitelist. Any authenticated user will be allowed.")

        # add whitelisted users to the db
        for name in whitelist:
            user = orm.User.find(db, name)
            if user is None:
                user = orm.User(name=name)
                new_users.append(user)
                db.add(user)

        db.commit()

        # Notify authenticator of all users.
        # This ensures Auth whitelist is up-to-date with the database.
        # This lets whitelist be used to set up initial list,
        # but changes to the whitelist can occur in the database,
        # and persist across sessions.
        for user in db.query(orm.User):
            try:
                yield gen.maybe_future(self.authenticator.add_user(user))
            except Exception:
                # TODO: Review approach to synchronize whitelist with db
                # known cause of the exception is a user who has already been removed from the system

def user_from_username(self, username):
        """Get User for username, creating if it doesn't exist"""
        user = self.find_user(username)
        if user is None:
            # not found, create and register user
            u = orm.User(name=username)
            self.db.add(u)
            self.db.commit()
            user = self._user_from_orm(u)
        return user

def user_from_username(self, username):
        """Get User for username, creating if it doesn't exist"""
        user = self.find_user(username)
        if user is None:
            # not found, create and register user
            u = orm.User(name=username)
            self.db.add(u)
            self.db.commit()
            user = self._user_from_orm(u)
        return user

]
        self.authenticator.whitelist = set(whitelist)  # force normalization
        for username in whitelist:
            if not self.authenticator.validate_username(username):
                raise ValueError("username %r is not valid" % username)

        if not whitelist:
            self.log.info(
                "Not using whitelist. Any authenticated user will be allowed."
            )

        # add whitelisted users to the db
        for name in whitelist:
            user = orm.User.find(db, name)
            if user is None:
                user = orm.User(name=name)
                new_users.append(user)
                db.add(user)

        db.commit()

        # Notify authenticator of all users.
        # This ensures Auth whitelist is up-to-date with the database.
        # This lets whitelist be used to set up initial list,
        # but changes to the whitelist can occur in the database,
        # and persist across sessions.
        for user in db.query(orm.User):
            try:
                await maybe_future(self.authenticator.add_user(user))
            except Exception:
                self.log.exception("Error adding user %s already in db", user.name)
                if self.authenticator.delete_invalid_users:

"""Load predefined groups into the database"""
        db = self.db
        for name, usernames in self.load_groups.items():
            group = orm.Group.find(db, name)
            if group is None:
                group = orm.Group(name=name)
                db.add(group)
            for username in usernames:
                username = self.authenticator.normalize_username(username)
                if not (yield gen.maybe_future(self.authenticator.check_whitelist(username))):
                    raise ValueError("Username %r is not in whitelist" % username)
                user = orm.User.find(db, name=username)
                if user is None:
                    if not self.authenticator.validate_username(username):
                        raise ValueError("Group username %r is not valid" % username)
                    user = orm.User(name=username)
                    db.add(user)
                group.users.append(user)
        db.commit()

"""Get the User for a given cookie, if there is one"""
        cookie_id = self.get_secure_cookie(
            cookie_name,
            cookie_value,
            max_age_days=self.cookie_max_age_days,
        )
        def clear():
            self.clear_cookie(cookie_name, path=self.hub.base_url)

        if cookie_id is None:
            if self.get_cookie(cookie_name):
                self.log.warning("Invalid or expired cookie token")
                clear()
            return
        cookie_id = cookie_id.decode('utf8', 'replace')
        u = self.db.query(orm.User).filter(orm.User.cookie_id==cookie_id).first()
        user = self._user_from_orm(u)
        if user is None:
            self.log.warning("Invalid cookie token")
            # have cookie, but it's not valid. Clear it and start over.
            clear()
            return
        # update user activity
        user.last_activity = datetime.utcnow()
        self.db.commit()
        return user

def get(self):
        data = [
            self.user_model(u, include_servers=True, include_state=True)
            for u in self.db.query(orm.User)
        ]
        self.write(json.dumps(data))

def user_model(self, user, include_servers=False, include_state=False):
        """Get the JSON model for a User object"""
        if isinstance(user, orm.User):
            user = self.users[user.id]

        model = {
            'kind': 'user',
            'name': user.name,
            'admin': user.admin,
            'groups': [g.name for g in user.groups],
            'server': user.url if user.running else None,
            'pending': None,
            'created': isoformat(user.created),
            'last_activity': isoformat(user.last_activity),
        }
        if '' in user.spawners:
            model['pending'] = user.spawners[''].pending

        if not include_servers: