code: def test_correct_results(self, gamma, invert_image, retain_stats):
      adjuster = AdjustContrastd(
          "img",
          gamma=gamma,
          invert_image=invert_image,
          retain_stats=retain_stats,
      )
      for p in TEST_NDARRAYS:
          result = adjuster({"img": p(self.imt)})
          if invert_image:
              self.imt = -self.imt
  
          if retain_stats:
              mn = self.imt.mean()
              sd = self.imt.std()
  
          epsilon = 1e-7
          img_min = self.imt.min()
          img_range = self.imt.max() - img_min
  
          expected = (
              np.power(
                  ((self.imt - img_min) / float(img_range + epsilon)),
                  gamma,
              )
              * img_range
              + img_min
          )
  
          if retain_stats:
              # zero mean and normalize
              expected = expected - expected.mean()
              expected = expected / (expected.std() + 1e-8)
              # restore old mean and standard deviation
              expected = sd * expected + mn
  
          if invert_image:
              expected = -expected
          assert_allclose(
              result["img"], expected, atol=1e-05, type_test="tensor"
          )
  
file_path: MONAI/tests/test_adjust_contrastd.py
imports: from __future__ import annotations
  import unittest
  import numpy
  from parameterized import parameterized
  from monai.transforms import AdjustContrastd
  from tests.utils import TEST_NDARRAYS, NumpyImageTestCase2D, assert_allclose
label_desc: Use image node_id 1 for calling the TestAdjustContrastd obj's underlying member method code with example usage: obj.test_correct_results(gamma, invert_image, retain_stats) without return types