class_docstr: GAN Dataset searchs for all the wav files under root path
  and converts them to acoustic features on the fly and returns
  random segments of (audio, feature) couples.
code: def __len__(self):
      return len(self.item_list)
  
file_path: TTS/TTS/vocoder/datasets/gan_dataset.py
imports: import os
  import glob
  import torch
  import random
  import numpy
  from torch.utils.data import Dataset
  from multiprocessing import Manager
label_desc: Use image node_id 4 for calling the GANDataset obj's underlying member method code with example usage: obj.__len__() and returns: len