you can see the
x = predict_transform(x, inp_dim, anchors, num_classes, CUDA)
the second parameter represents  input image dim。this value is 608 in yolov3.cfg,
but in the get_test_input()  function,the image is resized 416.so it confict.
img = cv2.resize(img, (416,416))
so you can change them same.
you have two choice