Converting a tensor to a python boolean might cause the trace to be incorrect. We can't record the data flow of python values
## Environment info
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     Don't forget to fill out the missing fields in that output! -->

- `transformers` version:
- Platform: CENTOS 8.
- Python version: 3.7
- PyTorch version (GPU?): 1.9.0 + cuda
- Tensorflow version (GPU?): No
- Using GPU in script?: No
- Using distributed or parallel set-up in script?: No

### Who can help
<!-- Your issue will be replied to more quickly if you can figure out the right person to tag with @
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 Please tag fewer than 3 people.
 @patrickvonplaten, @patil-suraj  @LysandreJik
Models:

- albert, bert, xlm: @LysandreJik
- blenderbot, bart, marian, pegasus, encoderdecoder,  t5: @patrickvonplaten, @patil-suraj
- longformer, reformer, transfoxl, xlnet: @patrickvonplaten
- fsmt: @stas00
- funnel: @sgugger
- gpt2: @patrickvonplaten, @LysandreJik
- rag: @patrickvonplaten, @lhoestq
- tensorflow: @Rocketknight1

Library:

- benchmarks: @patrickvonplaten
- deepspeed: @stas00
- ray/raytune: @richardliaw, @amogkam
- text generation: @patrickvonplaten
- tokenizers: @LysandreJik
- trainer: @sgugger
- pipelines: @LysandreJik

Documentation: @sgugger

Model hub:

- for issues with a model report at https://discuss.huggingface.co/ and tag the model's creator.

HF projects:

- datasets: [different repo](https://github.com/huggingface/datasets)
- rust tokenizers: [different repo](https://github.com/huggingface/tokenizers)

Examples:

- maintained examples (not research project or legacy): @sgugger, @patil-suraj
- research_projects/bert-loses-patience: @JetRunner
- research_projects/distillation: @VictorSanh

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## Information
![image](https://user-images.githubusercontent.com/26025961/126442774-d5833dbb-3ebb-4eeb-a12b-4a47141c9a74.png)
I convert the hugging face bart model to onnx model using transformer.onnx (thanks for the excellent tools). But these warnings occured and they may have a influencec on the performance of model. 


Hi @leoozy, you should safely disregard these warnings. The warnings should only apply to assertions we make to ensure that the input shape passed is correct.<|||||>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/master/CONTRIBUTING.md) are likely to be ignored.