code: def test_compute_mel_spectrogram(self):
      mel_featurizer = MelSpectrogramFeaturizer(
          mel_dim=self.spec_dim,
          hop_length=self.hop_len,
          sample_rate=self.sample_rate,
      )
  
      with self._create_test_dir() as test_dir:
          spec = mel_featurizer.compute_mel_spec(
              manifest_entry=self.manifest_entry, audio_dir=test_dir
          )
  
      assert len(spec.shape) == 2
      assert spec.dtype == np.float32
      assert spec.shape[0] == self.spec_dim
      assert spec.shape[1] == self.spec_len
  
imports: import contextlib
  import tempfile
  from pathlib import Path
  import numpy
  import pytest
  import soundfile
  import torch
  from nemo.collections.tts.parts.preprocessing.features import EnergyFeaturizer, MelSpectrogramFeaturizer, PitchFeaturizer
label_desc: Use image node_id 4 for calling the TestTTSFeatures obj's underlying member method code with example usage: obj.test_compute_mel_spectrogram() without return types