code: def test_neural_hmm_forward(self):
      (
          input_dummy,
          input_lengths,
          mel_spec,
          mel_lengths,
      ) = self._get_embedded_input()
      neural_hmm = self._get_neural_hmm()
      log_prob, log_alpha_scaled, transition_matrix, means = neural_hmm(
          input_dummy,
          input_lengths,
          mel_spec.transpose(1, 2),
          mel_lengths,
      )
      self.assertEqual(log_prob.shape, (input_dummy.shape[0],))
      self.assertEqual(log_alpha_scaled.shape, transition_matrix.shape)
  
imports: import os
  import random
  import unittest
  from copy import deepcopy
  import torch
  from tests import get_tests_output_path
  from TTS.tts.configs.overflow_config import OverflowConfig
  from TTS.tts.layers.overflow.common_layers import Encoder, Outputnet, OverflowUtils
  from TTS.tts.layers.overflow.decoder import Decoder
  from TTS.tts.layers.overflow.neural_hmm import EmissionModel, NeuralHMM, TransitionModel
  from TTS.tts.models.overflow import Overflow
  from TTS.tts.utils.helpers import sequence_mask
  from TTS.utils.audio import AudioProcessor
label_desc: Use image node_id 5 for calling the TestNeuralHMM obj's underlying member method code with example usage: obj.test_neural_hmm_forward() without return types