NLP部分的模型试验过程发现无法按照readme运行

## 环境
1.系统环境：MegStudio
2.MegEngine版本：
3.python版本：3.7
4.模型名称：bert cls mgpc

## 复现步骤
1. 下载models
2. 按照readme提示在MegStudio运行
3. 没有tuple

## 请提供关键的代码片段便于追查问题

## 请提供完整的日志及报错信息

Start with the README instructions for the bert cls mgpc model and reproduce the run in MegStudio using Python 3.7. Check the reported “no tuple” failure and compare the model's documented steps with the actual execution. Done means the README procedure runs successfully without that error, with the MegEngine version and complete log recorded.

Written by the indexing model from the issue text.