class_docstr: WaveRNN Dataset searchs for all the wav files under root path
  and converts them to acoustic features on the fly.
code: def __len__(self):
      return len(self.item_list)
  
file_path: TTS/TTS/vocoder/datasets/wavernn_dataset.py
imports: import torch
  import numpy
  from torch.utils.data import Dataset
label_desc: Use image node_id 2 for calling the WaveRNNDataset obj's underlying member method code with example usage: obj.__len__() and returns: len