model = nn.Sequential(
          nn.Conv2d(1, 16, kernel_size=(4, 4), stride=(2, 2), padding=(1, 1)),
          nn.ReLU(),
          nn.Conv2d(16, 32, kernel_size=(4, 4), stride=(2, 2), padding=(1, 1)),
          nn.ReLU()
        )

nn.Sequential(
    nn.Conv2d(1, 1, kernel_size=(4, 4), stride=(2, 2), padding=(1, 1)),
    *list(model.modules())[1:]
)


Sequential(
  (0): Conv2d(1, 1, kernel_size=(4, 4), stride=(2, 2), padding=(1, 1))
  (1): Conv2d(1, 16, kernel_size=(4, 4), stride=(2, 2), padding=(1, 1))
  (2): ReLU()
  (3): Conv2d(16, 32, kernel_size=(4, 4), stride=(2, 2), padding=(1, 1))
  (4): ReLU()
)