code: def test_prewhiten():
      rescaled_img = trainer.prewhiten(image_tensor).numpy()
      restored_img = (rescaled_img + 1) * 127.5
  
      assert np.allclose(restored_img, image_tensor.numpy(), 1e-3, 1e-3)
  
file_path: chitra/tests/test_trainer.py
imports: from unittest.mock import MagicMock
  import numpy
  import pytest
  import tensorflow
  from tensorflow import keras
  from chitra.trainer import Dataset, InterpretModel, Trainer, create_cnn
label_desc: Use image node_id 6 for calling a global function with example usage: test_prewhiten() without return types