“服务器”函数调用中的参数无值

Question

我想在discord.py机器人中制作一个关卡系统，但我总是遇到这些错误，而且我不知道该如何解决

void loadData() async {

 SharedPreferences sharedPreferences = await SharedPreferences.getInstance();
 final todoArray = _decodeTodoData(sharedPreferences.getStringList("savedTodo"))
 //This is your array :) -> todoArray    
}
List<Todo> _decodeTodoData(List<String> todos) {
    try {
      //Transforming List<String> to Json
      var result = todos.map((v) => json.decode(v)).toList();
      //Transforming the Json into Array<Todo>
      var todObjects = result.map((v) => Todo.fromJson(v)).toList();
      return todObjects;
    } catch (error) {
      return [];
    }
  }
}

同时显示的错误是： 函数调用中参数“ server”没有值

编辑： Update_data的定义如下：

@bot.event
async def on_member_join(member):
####the first error occurs here on update_data####
        await update_data(users, member)


@bot.event
async def on_message(message):
    with open("userslvl.json", "r") as f:
        users = json.load(f)

        if message.author.bot:
            return
        if message.channel.is_private:
            return
        else:
            await update_data(users, message.author, message.server)
            number = random.randint(5,10)
####the second error occurs here on add_experience####
            await add_experience(users, message.author, number, message.server)
            await level_up(users, message.author, message.channel, message.server)

        with open("userslvl.json", "w") as f:
            json.dump(users, f)
    await bot.process_commands(message)

和add_experience的定义如下：

    async def update_data(users, user, server):
        if not user.id + "-" + server.id in users:
            users[user.id + "-" + server.id] = {}
            users[user.id + "-" + server.id]["experience"] = 0
            users[user.id + "-" + server.id]["level"] = 1
            users[user.id + "-" + server.id]["last_message"] = 0