pytorch BN层报错：ValueError: expected 4D input (got 2D input)

    Traceback (most recent call last):
      File "train_noPfc.py", line 201, in <module>
    main(args_)
      File "train_noPfc.py", line 160, in main
    f_masked, focc_masked, output, output_occ, f_diff, out = backbone(img1, img2)
      File "/home/user1/miniconda3/lib/python3.7/site-packages/torch/nn/modules/module.py", line 727, in _call_impl
    result = self.forward(*input, **kwargs)
      File "/home/user1/miniconda3/lib/python3.7/site-packages/torch/nn/parallel/distributed.py", line 619, in forward
    output = self.module(*inputs[0], **kwargs[0])
      File "/home/user1/minicond