code: def test_denoise():
      """ """
      fdata, fbval, fbvec = dpd.get_fnames()
      # Test on 4D image:
      data, _ = load_nifti(fdata)
      sigma1 = estimate_sigma(data)
      nlmeans(data, sigma=sigma1)
  
      # Test on 3D image:
      data = data[..., 0]
      sigma2 = estimate_sigma(data)
      nlmeans(data, sigma=sigma2)
  
imports: from dipy.denoise.noise_estimate import estimate_sigma
  from dipy.denoise.nlmeans import nlmeans
  import dipy.data
  from dipy.io.image import load_nifti
label_desc: Use image node_id 1 for calling a global function with example usage: test_denoise() without return types