code: def test_spec_to_mel(self):
      mel_basis = np_transforms.build_mel_basis(**self.config)
      spec = np.random.rand(self.config.fft_size // 2 + 1, 20)  # [C, T]
      mel = np_transforms.spec_to_mel(spec=spec, mel_basis=mel_basis)
      self.assertEqual(mel.shape, (self.config.num_mels, 20))
  
imports: import math
  import os
  import unittest
  from dataclasses import dataclass
  import librosa
  import numpy
  from coqpit import Coqpit
  from tests import get_tests_input_path, get_tests_output_path, get_tests_path
  from TTS.utils.audio import numpy_transforms
label_desc: Use image node_id 6 for calling the TestNumpyTransforms obj's underlying member method code with example usage: obj.test_spec_to_mel() without return types