code: def loss_dec(self, dec, x_out, t_out, y_out, lam1=100, lam2=1):
      batchsize, _, w, h = y_out.shape
      loss_rec = lam1 * (F.mean_absolute_error(x_out, t_out))
      loss_adv = lam2 * F.sum(F.softplus(-y_out)) / batchsize / w / h
      loss = loss_rec + loss_adv
      chainer.report({"loss": loss}, dec)
      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 3 for calling the FacadeUpdater obj's underlying member method code with example usage: obj.loss_dec(dec, x_out, t_out, y_out, lam1, lam2) and returns: loss