class_docstr: GramVaaniConverter converts the mp3's to wav's for a GramVaani dataset.
  Args:
    target_dir (str): The path to download the data from
    mp3_directory (os.path): The path containing the GramVaani mp3's
  Attributes:
      target_dir (str): The target directory passed as a command line argument
      mp3_directory (os.path): The path containing the GramVaani mp3's
code: def _pre_convert(self):
      wav_directory = os.path.join(self.target_dir, "wav")
      if not os.path.exists(self.target_dir):
          _logger.info("Creating directory...%s", self.target_dir)
          os.mkdir(self.target_dir)
      if not os.path.exists(wav_directory):
          _logger.info("Creating directory...%s", wav_directory)
          os.mkdir(wav_directory)
      return wav_directory
  
imports: import csv
  import logging
  import math
  import os
  import subprocess
  import urllib
  from pathlib import Path
  import pandas
  from sox import Transformer
  import swifter
  from deepspeech_training.util.importers import get_importers_parser, get_validate_label
label_desc: Use image node_id 3 for calling the GramVaaniConverter obj's underlying member method code with example usage: obj._pre_convert() and returns: wav_directory