Need help to solve a runtime error
When I run the code, I keep getting the following error. Any suggestions would be appreciated!

Traceback (most recent call last):
  File "/root/PycharmProjects/Photo-Sketching/train.py", line 68, in <module>
    main()
  File "/root/PycharmProjects/Photo-Sketching/train.py", line 39, in main
    model.optimize_parameters()           # error
  File "/root/PycharmProjects/Photo-Sketching/models/pix2pix_model.py", line 139, in optimize_parameters
    self.backward_D()
  File "/root/PycharmProjects/Photo-Sketching/models/pix2pix_model.py", line 106, in backward_D
    pred_real = self.netD(real_AB)         # error------------------------------------------------
  File "/usr/local/lib/python3.5/dist-packages/torch/nn/modules/module.py", line 489, in __call__
    result = self.forward(*input, **kwargs)
  File "/root/PycharmProjects/Photo-Sketching/models/networks.py", line 423, in forward
    return self.model(input)
  File "/usr/local/lib/python3.5/dist-packages/torch/nn/modules/module.py", line 489, in __call__
    result = self.forward(*input, **kwargs)
  File "/usr/local/lib/python3.5/dist-packages/torch/nn/modules/container.py", line 92, in forward
    input = module(input)
  File "/usr/local/lib/python3.5/dist-packages/torch/nn/modules/module.py", line 489, in __call__
    result = self.forward(*input, **kwargs)
  File "/usr/local/lib/python3.5/dist-packages/torch/nn/modules/conv.py", line 320, in forward
    self.padding, self.dilation, self.groups)
RuntimeError: Given groups=1, weight of size [64, 6, 4, 4], expected input[1, 4, 256, 256] to have 6 channels, but got 4 channels instead