torch模型的forward方法里面内容为空，用Electra模型无法训练。
![image](https://user-images.githubusercontent.com/41299010/89173067-406ef880-d5b6-11ea-9c64-4e41243dad43.png)
![image](https://user-images.githubusercontent.com/41299010/89173121-5a104000-d5b6-11ea-9039-d2341dca9463.png)
上图是训练模型时调用的forward方法，这个方法里的代码为空，下图是报的错，请教您这个问题该如何解决？非常感谢您！！！
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