code: def decode_mu_law(y, mu=256):
      """Perform mu-law decoding.
  
      Args:
          x (ndarray): Quantized audio signal with the range from 0 to mu - 1.
          mu (int): Quantized level.
  
      Returns:
          ndarray: Audio signal with the range from -1 to 1.
  
      """
      mu = mu - 1
      fx = (y - 0.5) / mu * 2 - 1
      x = np.sign(fx) / mu * ((1 + mu) ** np.abs(fx) - 1)
      return x
  
imports: import logging
  import sys
  import time
  import numpy
  import torch
  import torch.nn.functional
  from torch import nn
label_desc: Use image node_id 2 for calling a global function with example usage: decode_mu_law(y, mu) and returns: x