code: def test_spectrogram(self):
      mel_spectrogram = AudioLoader.load_mel_spectrogram(
          self.sample_wav_file, n_mels=128
      )
  
      flow = naf.Sequential(
          [
              nas.FrequencyMaskingAug(stateless=False),
              nas.TimeMaskingAug(stateless=False),
              nas.TimeMaskingAug(stateless=False),
          ]
      )
  
      augmented_mel_spectrograms = flow.augment(mel_spectrogram)
  
      for aug in flow:
          if aug.name == "FrequencyMasking_Aug":
              aug_data = augmented_mel_spectrograms[0][
                  aug.f0 : aug.f0 + aug.f, aug.time_start : aug.time_end
              ]
              orig_data = mel_spectrogram[
                  aug.f0 : aug.f0 + aug.f, aug.time_start : aug.time_end
              ]
  
              self.assertEqual(
                  orig_data.size, np.count_nonzero(orig_data)
              )
              self.assertEqual(0, np.count_nonzero(aug_data))
          elif aug.name == "TimeMasking_Aug":
              self.assertEqual(
                  len(mel_spectrogram[:, aug.t0]),
                  np.count_nonzero(mel_spectrogram[:, aug.t0]),
              )
              self.assertEqual(
                  0,
                  np.count_nonzero(
                      augmented_mel_spectrograms[0][:, aug.t0]
                  ),
              )
          else:
              raise ValueError(
                  "Unexpected flow for {} augmenter".format(aug.name)
              )
  
      self.assertTrue(len(flow) > 0)
  
file_path: nlpaug/test/flow/test_sequential.py
imports: import unittest
  import os
  import numpy
  from dotenv import load_dotenv
  import nlpaug.augmenter.char
  import nlpaug.augmenter.word
  import nlpaug.augmenter.spectrogram
  import nlpaug.augmenter.audio
  import nlpaug.flow
  from nlpaug.util import Action, AudioLoader
label_desc: Use image node_id 5 for calling the TestSequential obj's underlying member method code with example usage: obj.test_spectrogram() without return types