code: def update(self, arr):
      batch_mean = np.mean(arr, axis=0)
      batch_var = np.var(arr, axis=0)
      batch_count = arr.shape[0]
      self.update_from_moments(batch_mean, batch_var, batch_count)
  
imports: import numpy
label_desc: Use image node_id 2 for calling the RunningMeanStd obj's underlying member method code with example usage: obj.update(arr) without return types