Exporting mt5 model to onnx, changes the output size of model

I am trying to export mt5 model to onnx. Since onnx model is large than 2GB, its required to export model via use_external_data_format=True in torch.onnx.export. Exporting model works, it saves weights into small binary files but i also see the output shape is changed. Can ideas to get output shape as pytorch model??