code: def test_combine_stds(
      samples, sample_means, sample_stds, expected_std
  ):
      num_sents = [len(l) for l in samples]
      combined_std = utils.combine_stds(
          sample_stds, sample_means, num_sents
      )
      assert np.isclose(expected_std, combined_std)
  
imports: import gzip
  import math
  import os
  import re
  from tempfile import TemporaryDirectory
  import unittest
  import numpy
  import pytest
  import torch
  from sockeye import __version__
  from sockeye import constants
  from sockeye import utils
label_desc: Use image node_id 13 for calling a global function with example usage: test_combine_stds(samples, sample_means, sample_stds, expected_std) without return types