老师，麻烦帮我看一下，我的代码运行不出来，报错name 'self' is not defined, 谢谢！

# coding:utf-8

import os
import time
import json

from common.utils import check_file
from common.error import UserExistsError


class Base(object):
    def __init__(self, user_json, gift_json):
        self.user_json = user_json
        self.gift_json = gift_json

        self.__check_user_json()
        self.__check_gift_json()

    def __check_user_json(self):
        check_file(self.user_json)

    def __check_gift_json(self):
        check_file(self.gift_json)

    def __read_users(self, time_to_str=False):
        with open(self.user_json, 'r') as f:
            data = json.loads(f.read())
        return data

    def __write_user(self, **user):  # password active
        if 'username' not in user:
            raise ValueError('missing username')
        if 'role' not in user:
            raise ValueError('missing role')

        user['active'] = True
        user['create_time'] = time.time()
        user['update_time'] = time.time()
        user['gifts'] = []

        users = self.__read_users()

        if user['username'] in users:
            raise UserExistsError('username %s had exists' % user['username'])

        users.update(
            {user['username']: user}
        )
        json_user = json.dumps(users)
        with open(self.user_json, 'w') as f:
            f.write(json_user)


if __name__ == '__main__':

    gift_path = os.path.join(os.getcwd(), 'storage', 'gift.json')
    user_path = os.path.join(os.getcwd(), 'storage', 'user.json')
    print(gift_path)
    print(user_path)
    base = Base(user_json=user_path, gift_json=gift_path)
    base.write_user(username='Bob', role='admin')