layoutxlm model can not convert to onnx
### Model description

I use layoutxlm to training my data for downstream, when I convert the model which I trained to onnx by huggingface code layoutlmv2-to-onnx, it occurs below problem, can you give me some advice? it seems concat two different types causing this problem, but I do not modify any code just using run xfun for token classification, which confused me so much, I hope you can help us


### Open source status

- [ ] The model implementation is available
- [ ] The model weights are available

### Provide useful links for the implementation

I use layoutxlm to training my data for downstream, when I convert the model which I trained to onnx by huggingface code layoutlmv2-to-onnx, it occurs below problem, can you give me some advice? it seems concat two different types causing this problem, but I do not modify any code just using run xfun for token classification, which confused me so much, I hope you can help us
<img width="943" alt="企业微信截图_1656080658142" src="https://user-images.githubusercontent.com/77612906/175556272-af5e91d0-c76e-483f-ad24-95fa7690146e.png">

cc @lewtun<|||||>This issue has been automatically marked as stale because it has not had recent activity. If you think this still needs to be addressed please comment on this thread.

Please note that issues that do not follow the [contributing guidelines](https://github.com/huggingface/transformers/blob/main/CONTRIBUTING.md) are likely to be ignored.<|||||>@lewtun  friendly ping!<|||||>This issue has been automatically marked as stale because it has not had recent activity. If you think this still needs to be addressed please comment on this thread.

Please note that issues that do not follow the [contributing guidelines](https://github.com/huggingface/transformers/blob/main/CONTRIBUTING.md) are likely to be ignored.