is nn.gModule for input not valid?

[zlqhem]

I have a CNN model and call forward() method.

model = torch.load("./mymodel.net")
input = torch.load("./input.bin")
out =  model:forward(input)

When I pass it to torch2caffe.lua, it complains that is a unknown Torch class <nn.gModule>.
Is it illegal use?

$ th torch2caffe/torch2caffe.lua --input <path>/mymodel.net
Opts: %s	{
  prototxt = "",
  format = "lua",
  input = "<path>/mymodel.net",
  caffemodel = "",
  preprocessing = "",
  input_dims = {
    0
  },
  verify = "",
  input_tensor = ""
}	
<mypath>/torch/install/bin/luajit: ...<mypath>/torch/install/share/lua/5.1/torch/File.lua:343: unknown Torch class <nn.gModule>
stack traceback: