Unsupported output type of N11onnxruntime22SequenceTensorTypeBaseE. Can't constant fold SequenceEmpty node 'SequenceEmpty_5330'
Author: will-wiki
Pull request: no

## Environment
- `transformers` version:4.16.0.dev0
- Platform:centos7
- Python version:3.6.5
- PyTorch version (GPU?):1.10.1
- CUDA:10.2
- Cudnn:7.65

Models:

- T5, BART, Marian, Pegasus, EncoderDecoder: @patrickvonplaten

Library:

- Text generation: @patrickvonplaten @narsil


## Information

The problem arises when using:
* [[ ] the official example scripts: (give details below)](https://github.com/huggingface/transformers/tree/v4.15.0/examples/onnx/pytorch/summarization)

## Add
Thank you very much for your open source code! I encountered the following problems when using the official code to convert BART into onnx model. 

Debug info:
2022-01-28 15:48:27.150774771 [W:onnxruntime:, graph.cc:3526 CleanUnusedInitializersAndNodeArgs] Removing initializer '1751'. It is not used by any node and should be removed from the model.
2022-01-28 15:48:27.309347842 [W:onnxruntime:, graph.cc:3526 CleanUnusedInitializersAndNodeArgs] Removing initializer '5836'. It is not used by any node and should be removed from the model.
2022-01-28 15:48:27.309405007 [W:onnxruntime:, graph.cc:3526 CleanUnusedInitializersAndNodeArgs] Removing initializer '5882'. It is not used by any node and should be removed from the model.
2022-01-28 15:48:27.309424807 [W:onnxruntime:, graph.cc:3526 CleanUnusedInitializersAndNodeArgs] Removing initializer '5790'. It is not used by any node and should be removed from the model.
2022-01-28 15:48:27.322407481 [W:onnxruntime:, constant_folding.cc:202 ApplyImpl] Unsupported output type of N11onnxruntime22SequenceTensorTypeBaseE. Can't constant fold SequenceEmpty node 'SequenceEmpty_5330'
2022-01-28 15:48:27.322776093 [W:onnxruntime:, constant_folding.cc:202 ApplyImpl] Unsupported output type of N11onnxruntime22SequenceTensorTypeBaseE. Can't constant fold SequenceEmpty node 'SequenceEmpty_808'
2022-01-28 15:48:27.322825883 [W:onnxruntime:, constant_folding.cc:202 ApplyImpl] Unsupported output type of N11onnxruntime22SequenceTensorTypeBaseE. Can't constant fold SequenceEmpty node 'SequenceEmpty_1'
2022-01-28 15:48:27.326471594 [W:onnxruntime:, constant_folding.cc:202 ApplyImpl] Unsupported output type of N11onnxruntime22SequenceTensorTypeBaseE. Can't constant fold SequenceEmpty node 'SequenceEmpty_5128'
2022-01-28 15:48:27.362769188 [W:onnxruntime:, constant_folding.cc:202 ApplyImpl] Unsupported output type of N11onnxruntime22SequenceTensorTypeBaseE. Can't constant fold SequenceEmpty node 'SequenceEmpty_5330'
2022-01-28 15:48:27.363078495 [W:onnxruntime:, constant_folding.cc:202 ApplyImpl] Unsupported output type of N11onnxruntime22SequenceTensorTypeBaseE. Can't constant fold SequenceEmpty node 'SequenceEmpty_808'
2022-01-28 15:48:27.363121543 [W:onnxruntime:, constant_folding.cc:202 ApplyImpl] Unsupported output type of N11onnxruntime22SequenceTensorTypeBaseE. Can't constant fold SequenceEmpty node 'SequenceEmpty_1'
2022-01-28 15:48:27.366445273 [W:onnxruntime:, constant_folding.cc:202 ApplyImpl] Unsupported output type of N11onnxruntime22SequenceTensorTypeBaseE. Can't constant fold SequenceEmpty node 'SequenceEmpty_5128'
2022-01-28 15:48:27.429176464 [W:onnxruntime:, constant_folding.cc:202 ApplyImpl] Unsupported output type of N11onnxruntime22SequenceTensorTypeBaseE. Can't constant fold SequenceEmpty node 'SequenceEmpty_5330'
2022-01-28 15:48:27.429415152 [W:onnxruntime:, constant_folding.cc:202 ApplyImpl] Unsupported output type of N11onnxruntime22SequenceTensorTypeBaseE. Can't constant fold SequenceEmpty node 'SequenceEmpty_808'
2022-01-28 15:48:27.429447650 [W:onnxruntime:, constant_folding.cc:202 ApplyImpl] Unsupported output type of N11onnxruntime22SequenceTensorTypeBaseE. Can't constant fold SequenceEmpty node 'SequenceEmpty_1'
2022-01-28 15:48:27.431914509 [W:onnxruntime:, constant_folding.cc:202 ApplyImpl] Unsupported output type of N11onnxruntime22SequenceTensorTypeBaseE. Can't constant fold SequenceEmpty node 'SequenceEmpty_5128'
2022-01-28 15:48:27.570257513 [W:onnxruntime:, graph.cc:3526 CleanUnusedInitializersAndNodeArgs] Removing initializer '5152'. It is not used by any node and should be removed from the model.
2022-01-28 15:48:27.570293380 [W:onnxruntime:, graph.cc:3526 CleanUnusedInitializersAndNodeArgs] Removing initializer '5149'. It is not used by any node and should be removed from the model.





Comments:
Pinging @mfuntowicz for the onnx export.

Add
This error runs fine under onnxruntime, but when deployed to Tensorrt, it will not paser onnx model

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