Thnn_fused_gru_cell does not exist

When I export onnx model using GRUCell, I got a warning:

UserWarning: ONNX export failed on ATen operator _thnn_fused_gru_cell because torch.onnx.symbolic_opset10._thnn_fused_gru_cell does not exist
KeyError: '_thnn_fused_gru_cell'

and I failed to export, Anyone can give some advice?