code: def _normalize(self, x):
      if self.subtract_last:
          x = x - self.last
      else:
          x = x - self.mean
      x = x / self.stdev
      if self.affine:
          x = x * self.affine_weight
          x = x + self.affine_bias
      return x
  
imports: import math
  import numpy
  from typing import Optional
  import torch
  import torch.nn
  import torch.nn.functional
  from ..common._base_windows import BaseWindows
  from ..losses.pytorch import MAE
label_desc: Use image node_id 5 for calling the RevIN obj's underlying member method code with example usage: obj._normalize(x) and returns: x