code: def test_label_to_bow():
      labels = pt.tensor(
          [
              [1, 3],
              [0, 0],
          ]
      )
      bow = sockeye.loss._label_to_bow(labels, num_labels=4)
      expected_bow = pt.tensor(
          [
              [0, 1, 0, 1],
              [1, 0, 0, 0],
          ],
          dtype=pt.float32,
      )
      pt.testing.assert_close(bow, expected_bow)
  
file_path: sockeye/test/unit/test_loss.py
imports: import math
  import numpy
  import pytest
  import torch
  import sockeye.constants
  import sockeye.loss
  import sockeye.model
  import sockeye.utils
label_desc: Use image node_id 4 for calling a global function with example usage: test_label_to_bow() without return types