class_docstr: Base class of audio datasets, providing common functionality
  for other audio datasets.
  
  Args:
      collection: Collection of audio examples prepared from manifest files.
      audio_processor: Used to process every example from the collection.
                       A callable with `process` method. For reference,
                       please check ASRAudioProcessor.
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docstr: Return a single example from the dataset.
  
  Args:
      index: integer index of an example in the collection
  
  Returns:
      Dictionary providing mapping from signal to its tensor.
      For example:
      ```
      {
          'input_signal': input_signal_tensor,
          'target_signal': target_signal_tensor,
      }
      ```
code: def __getitem__(self, index: int) -> Dict[str, torch.Tensor]:
      """Return a single example from the dataset.
  
      Args:
          index: integer index of an example in the collection
  
      Returns:
          Dictionary providing mapping from signal to its tensor.
          For example:
          ```
          {
              'input_signal': input_signal_tensor,
              'target_signal': target_signal_tensor,
          }
          ```
      """
      example = self.collection[index]
      output = self.audio_processor.process(example=example)
  
      return output
  
imports: import abc
  import math
  import random
  from collections import OrderedDict, namedtuple
  from dataclasses import dataclass
  from typing import Callable, Dict, List, Optional, Tuple, Type, Union
  import librosa
  import numpy
  import torch
  from nemo.collections.asr.parts.preprocessing.segment import AudioSegment
  from nemo.collections.asr.parts.utils.audio_utils import ChannelSelectorType
  from nemo.collections.common.parts.preprocessing import collections
  from nemo.collections.common.parts.utils import flatten
  from nemo.core.classes import Dataset
  from nemo.core.neural_types import AudioSignal, EncodedRepresentation, LengthsType, NeuralType
  from nemo.utils import logging
label_desc: Use image node_id 4 for calling the BaseAudioDataset obj's underlying member method code with example usage: obj.__getitem__(index) and returns: output