code: def test_stack_tensors(self):
      tensors = [torch.ones([2]), torch.ones([4]), torch.ones([3])]
      max_lens = [6]
      expected_output = torch.tensor(
          [[1, 1, 0, 0, 0, 0], [1, 1, 1, 1, 0, 0], [1, 1, 1, 0, 0, 0]],
          dtype=torch.float32,
      )
  
      stacked_tensor = stack_tensors(tensors=tensors, max_lens=max_lens)
  
      torch.testing.assert_close(stacked_tensor, expected_output)
  
imports: from pathlib import Path
  import librosa
  import numpy
  import pytest
  import torch
  from nemo.collections.tts.parts.utils.tts_dataset_utils import filter_dataset_by_duration, get_abs_rel_paths, get_audio_filepaths, load_audio, normalize_volume, stack_tensors
label_desc: Use image node_id 13 for calling the TestTTSDatasetUtils obj's underlying member method code with example usage: obj.test_stack_tensors() without return types