Something wrong in using ToTensor()

During the process of dataloader(num_workers = 4), the program has no response when using ToTensor() to transform an image into a tensor.
Even after waiting a long time, there is still no response.

The image is in 'TIFF' format and converted to 'RGB'. The code is as follows:
feed_dict.image = Image.open(osp.join(self.image_root, feed_dict.image_filename)).convert('RGB')