code: def _create_fwd_inputs_outputs(self, inputs, outputs):
      # fwd_inputs: x_1, ..., x_n
      # fwd_outputs: y
      oshape = inputs[0].shape
      inputs_fwd = []
      for xshape in self.xshapes:
          input_fwd = nn.Variable(xshape, need_grad=True)
          inputs_fwd.append(input_fwd)
      outputs_fwd = [nn.Variable(oshape)]
      return inputs_fwd, outputs_fwd
  
imports: import nnabla
  import nnabla.function
  import nnabla.functions
  from nnabla.function import PythonFunction
label_desc: Use image node_id 4 for calling the ConcatenateDataGrad obj's underlying member method code with example usage: obj._create_fwd_inputs_outputs(inputs, outputs) and returns: inputs_fwd,  outputs_fwd