class_docstr: This class implements gain augmentation for audio.
code: def __repr__(self):
      return "{}(gain_levels={})".format(
          self.__class__.__name__, self.gain_levels
      )
  
imports: import argparse
  import math
  import pathlib
  import random
  from typing import Callable, Dict, List, Optional, Union
  import torch
  import torchaudio
  from data.transforms import TRANSFORMATIONS_REGISTRY, BaseTransformation
  from data.transforms.audio_aux import mfccs
label_desc: Use image node_id 4 for calling the Gain obj's underlying member method code with example usage: obj.__repr__() and returns: str