code: def normalize(tensor, stats):
      """
      normalize a tensor using a running mean and std
  
      :param tensor: (TensorFlow Tensor) the input tensor
      :param stats: (RunningMeanStd) the running mean and std of the input to normalize
      :return: (TensorFlow Tensor) the normalized tensor
      """
      if stats is None:
          return tensor
      return (tensor - stats.mean) / stats.std
  
imports: from functools import reduce
  import os
  import time
  from collections import deque
  import pickle
  import warnings
  import gym
  import numpy
  import tensorflow
  import tensorflow.contrib
  from mpi4py import MPI
  from stable_baselines import logger
  from stable_baselines.common import tf_util, OffPolicyRLModel, SetVerbosity, TensorboardWriter
  from stable_baselines.common.vec_env import VecEnv
  from stable_baselines.common.mpi_adam import MpiAdam
  from stable_baselines.common.buffers import ReplayBuffer
  from stable_baselines.common.math_util import unscale_action, scale_action
  from stable_baselines.common.mpi_running_mean_std import RunningMeanStd
  from stable_baselines.ddpg.policies import DDPGPolicy
label_desc: Use image node_id 1 for calling a global function with example usage: normalize(tensor, stats) and returns: unknown, tensor