code: def transform(self, x):
      x = x.astype(self.float_type)
      y = (
          numpy.sign(x)
          * numpy.log(1 + self.mu * numpy.abs(x))
          / numpy.log(1 + self.mu)
      )
      y = numpy.digitize(y, 2 * numpy.arange(self.mu) / self.mu - 1) - 1
      return y.astype(self.int_type)
  
file_path: chainer/examples/wavenet/utils.py
imports: import random
  import librosa
  import numpy
  import chainer
label_desc: Use image node_id 2 for calling the MuLaw obj's underlying member method code with example usage: obj.transform(x) and returns: y