code: def normalize(signal):
      """normalize signal
      Args:
          signal(FloatTensor): signal to be normalized.
      """
      signal_minusmean = signal - signal.mean()
      return signal_minusmean / signal_minusmean.abs().max()
  
imports: import io
  import os
  from typing import Dict, List, Optional, Union
  import torch
  import webdataset
  from nemo.collections.asr.data.audio_to_text import cache_datastore_manifests, expand_sharded_filepaths
  from nemo.collections.asr.parts.preprocessing.features import WaveformFeaturizer
  from nemo.collections.asr.parts.preprocessing.segment import available_formats
  from nemo.collections.common.parts.preprocessing import collections
  from nemo.core.classes import Dataset, IterableDataset
  from nemo.core.neural_types import AudioSignal, LabelsType, LengthsType, NeuralType, RegressionValuesType
  from nemo.utils import logging
label_desc: Use image node_id 2 for calling a global function with example usage: normalize(signal) and returns: unknown