[onnx export]UserWarning: Exporting aten::index operator with indices of type Byte

I am trying to convert a model to onnx in pytorch. But I got warning :
C:\Users\xiaoj\.conda\envs\yolact_clone\lib\site-packages\torch\onnx\symbolic_opset9.py:2691: UserWarning: Exporting aten::index operator with indices of type Byte. Only 1-D indices are supported. In any other case, this will produce an incorrect ONNX graph. warnings.warn("Exporting aten::index operator with indices of type Byte. "

After some research i found this pytorch/symbolic_opset9.py at master · pytorch/pytorch · GitHub
But I still not sure how to fix this warning.
Please help.