WARNING:root:ONNX is running on CPU - you need to install CUDA/onnxruntime-gpu to run on GPU

The code I run:
```
import os
import json
from copy import deepcopy
os.environ["BACKEND"] = "onnx"
import onnxruntime as ort
from unisim import TextSim
```
I got message: `WARNING:root:ONNX is running on CPU - you need to install CUDA/onnxruntime-gpu to run on GPU`.

However, `ort.get_devices()` gives "GPU".

How can I fix it? Many thanks in advance.


