code: def _trigger(self):
      idx = 0
      for iA, iB in self.val_ds:
          vizA, vizB = self.pred(iA, iB)
          self.trainer.monitors.put_image("testA-{}".format(idx), vizA)
          self.trainer.monitors.put_image("testB-{}".format(idx), vizB)
          idx += 1
  
imports: import argparse
  import glob
  import os
  import tensorflow
  from six.moves import range
  from tensorpack import *
  from tensorpack.tfutils.scope_utils import auto_reuse_variable_scope
  from tensorpack.tfutils.summary import add_moving_summary
  from GAN import GANModelDesc, GANTrainer
label_desc: Use image node_id 3 for calling the VisualizeTestSet obj's underlying member method code with example usage: obj._trigger() without return types