code: def test_scalar_sigma(rng):
      S0 = 100 + np.zeros((20, 20, 20))
      noise = 2 * rng.standard_normal((20, 20, 20))
      S0 += noise
      S0[:10, :10, :10] = 300 + noise[:10, :10, :10]
  
      assert_raises(
          ValueError, non_local_means, S0, sigma=noise, rician=False
      )
  
file_path: dipy/dipy/denoise/tests/test_non_local_means.py
imports: import numpy
  from numpy.testing import assert_, assert_equal, assert_array_almost_equal, assert_raises
  from dipy.denoise.non_local_means import non_local_means
  from dipy.testing.decorators import set_random_number_generator
label_desc: Use image node_id 3 for calling a global function with example usage: test_scalar_sigma(rng) without return types