class_docstr: Base class of speech dataset.
class_docstr_tok: ["Base","class","of","speech","dataset","."]
code: def _read_file(self, input_file: str):
      raise NotImplementedError
  
imports: import csv
  import io
  import os
  from typing import Dict, List, Optional, Tuple, Union
  import numpy
  import paddle
  from paddlehub.utils.utils import extract_melspectrogram
label_desc: Use image node_id 2 for calling the BaseAudioDataset obj's underlying member method code with example usage: obj._read_file(input_file) without return types