class_docstr: Calculating running mean and variance
  https://en.wikipedia.org/wiki/Algorithms_for_calculating_variance#Parallel_algorithm
class_docstr_tok: ["Calculating","running","mean","and","variance","https",":","\/\/en.wikipedia.org\/wiki\/Algorithms_for_calculating_variance","#","Parallel_algorithm"]
code: def update(self, x):
      batch_mean = np.mean(x, axis=0)
      batch_var = np.var(x, axis=0)
      batch_count = x.shape[0]
      self.update_from_moments(batch_mean, batch_var, batch_count)
  
imports: import numpy
  import gym
  import time
  from parl.env.compat_wrappers import CompatWrapper
label_desc: Use image node_id 2 for calling the RunningMeanStd obj's underlying member method code with example usage: obj.update(x) without return types