You are passing the PIL.Image directly to the model as the input, which won’t work, since a tensor is expected:
image = Image.open("/content/drive/My Drive/volkswagen-beetle-2017-1280-01-1536873547.jpg").convert('RGB')
                
rgb_mean = np.mean(image, axis=(0, 1))
rgb_std = np.std(image, axis=(0, 1))
attention_maps, _, output1 = model(image)

You could either use the val_loader or transform the PIL.Image to a tensor using the transform_test transformation.