Optimizing mbart model: ValueError: Message onnx.ModelProto exceeds maximum protobuf size of 2GB: 3468757994

Describe the bug
python -m onnxruntime.transformers.optimizer --input "/home/sysadmin/downlaod/onnx_models/nmbart/model.onnx" --output ${export_model_path} --num_heads 16 --hidden_size 1024 --float16 --input 32 --use_gpu --opt_level 99 --use_external_data_format

I am trying to optimizing the Mbart model with the above commond, But this error occurs
Urgency
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System information

• OS Platform and Distribution (e.g., Linux Ubuntu 16.04):
• ONNX Runtime installed from (source or binary):
• ONNX Runtime version:
• Python version:
• Visual Studio version (if applicable):
• GCC/Compiler version (if compiling from source):
• CUDA/cuDNN version:
• GPU model and memory:

To Reproduce

• Describe steps/code to reproduce the behavior.
• Attach the ONNX model to the issue (where applicable) to expedite investigation.

Expected behavior
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Screenshots
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Additional context
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Start with the reported python -m onnxruntime.transformers.optimizer command and its --use_external_data_format option, then reproduce the failure using the referenced mBART ONNX model. Review the optimizer's handling of models exceeding the protobuf size limit; done means the cause and supported behavior are established with a reproducible result.