code: def test_spherical_area():
      # test the co_labelling functionality
      points, area = sphere_density(100)
      assert np.abs(area.sum() - 4 * np.pi) < 1.0e-2
  
file_path: nipy/nipy/algorithms/clustering/tests/test_vmm.py
imports: from unittest import skipIf
  import numpy
  from nibabel.optpkg import optional_package
  from ..von_mises_fisher_mixture import VonMisesMixture, select_vmm, select_vmm_cv, sphere_density
label_desc: Use image node_id 1 for calling a global function with example usage: test_spherical_area() without return types