class_docstr: This class uses a `RunnerMultiGPU` object to train a model on multiple
  GPUs. It mainly overrides the `_create_train_graph` to create a graph
  for adversarial training on multiple GPUs.
class_docstr_tok: ["This","class","uses","a","`","RunnerMultiGPU","`","object","to","train","a","model","on","multiple","GPUs",".","It","mainly","overrides","the","`","_create_train_graph","`","to","create","a","graph","for","adversarial","training","on","multiple","GPUs","."]
code: def _sync_params(self, forced=False):
      if forced or (self.step_num % self.hparams.sync_step == 0):
          self.sess.run(self.sync_ops)
  
imports: from collections import OrderedDict
  import logging
  import math
  import time
  import os
  import numpy
  import six
  import tensorflow
  from cleverhans.utils_tf import batch_indices
  from cleverhans.utils_mnist import data_mnist
  import utils_cifar
  import utils_svhn
  from utils import preprocess_batch
  from make_model import make_model
  from evaluator import Evaluator
  from evaluator import create_adv_by_name
  from model import clone_variable
label_desc: Use image node_id 4 for calling the TrainerMultiGPU obj's underlying member method code with example usage: obj._sync_params(forced) without return types