docstr: Test loading a signal from a file and apply silence perturbation
          
docstr_tok: ["Test","loading","a","signal","from","a","file","and","apply","silence","perturbation"]
code: def test_silence_perturb(self):
      """Test loading a signal from a file and apply silence perturbation"""
      with tempfile.TemporaryDirectory() as test_dir:
          # Prepare a wav file
          audio_file = os.path.join(test_dir, "audio.wav")
          # samples is a one-dimensional vector for single-channel signal
          samples = np.random.rand(self.num_samples)
          sf.write(audio_file, samples, self.sample_rate, "float")
  
          dur = 2
          perturber = SilencePerturbation(
              min_start_silence_secs=dur,
              max_start_silence_secs=dur,
              min_end_silence_secs=dur,
              max_end_silence_secs=dur,
          )
  
          audio = AudioSegment.from_file(audio_file)
          ori_audio_len = len(audio._samples)
          _ = perturber.perturb(audio)
  
          assert (
              len(audio._samples)
              == ori_audio_len + 2 * dur * self.sample_rate
          )
  
file_path: NeMo/tests/collections/asr/test_preprocessing_segment.py
imports: import json
  import os
  import tempfile
  from typing import List, Type, Union
  import numpy
  import pytest
  import soundfile
  from nemo.collections.asr.parts.preprocessing.perturb import NoisePerturbation, SilencePerturbation
  from nemo.collections.asr.parts.preprocessing.segment import AudioSegment
  from nemo.collections.asr.parts.utils.audio_utils import select_channels
label_desc: Use image node_id 5 for calling the TestAudioSegment obj's underlying member method code with example usage: obj.test_silence_perturb() without return types