code: def test_no_change_source(self):
      data = AudioLoader.load_mel_spectrogram(
          self.sample_wav_file, n_mels=128
      )
      aug = nas.FrequencyMaskingAug()
      aug_data = aug.augment(data)
      aug_audio = aug_data[0]
  
      comparison = data == aug_audio
      self.assertFalse(comparison.all())
  
file_path: nlpaug/test/augmenter/spectrogram/test_frequency_masking.py
imports: import unittest
  import os
  import numpy
  from dotenv import load_dotenv
  from nlpaug.util import AudioLoader
  import nlpaug.augmenter.spectrogram
label_desc: Use image node_id 3 for calling the TestFrequencyMasking obj's underlying member method code with example usage: obj.test_no_change_source() without return types