code: def loss_dis(self, dis, y_in, y_out):
      batchsize, _, w, h = y_in.shape
  
      L1 = F.sum(F.softplus(-y_in)) / batchsize / w / h
      L2 = F.sum(F.softplus(y_out)) / batchsize / w / h
      loss = L1 + L2
      chainer.report({"loss": loss}, dis)
      return loss
  
file_path: chainer/examples/pix2pix/updater.py
imports: from __future__ import print_function
  import chainer
  import chainer.functions
label_desc: Use image node_id 4 for calling the FacadeUpdater obj's underlying member method code with example usage: obj.loss_dis(dis, y_in, y_out) and returns: loss