main_test.py got a COCO score in effect, but demo.py didn't get any predictions

[aimhabo]

rt, I trained it about 12 epochs. And got COCO score main_test.py from 7 to 12(epochs).
But when I try to have a sight of predictions like 'python demo.py --cfg configs/faster/sniper_res50_e2e.yml', the result image in ./data/demo/ contains no bbox.