code: def forward(self, x: List[Tensor]):
      x = torch.stack(x)
      x = torch.sum(
          x, dim=0
      )  # above two act as interactive layer, CAddTable
      x = self.sigmoid(x)
      return x
  
file_path: BigDL/python/ppml/example/pytorch_nn_lr/pytorch_nn_lr_1.py
imports: import logging
  from typing import List
  import numpy
  import pandas
  import click
  import torch
  from torch import Tensor, nn
  from bigdl.ppml.fl.estimator import Estimator
  from bigdl.ppml.fl.nn.fl_context import init_fl_context
  from bigdl.ppml.fl.psi.psi_client import PSI
label_desc: Use image node_id 2 for calling the ServerModel obj's underlying member method code with example usage: obj.forward(x) and returns: x