code: def test_multivox_dsi():
      data, gtab = dsi_voxels()
      DS = DiffusionSpectrumModel(gtab)
  
      DSfit = DS.fit(data)
      PDF = DSfit.pdf()
      assert_equal(data.shape[:-1] + (17, 17, 17), PDF.shape)
      assert_equal(np.all(np.isreal(PDF)), True)
  
file_path: dipy/dipy/reconst/tests/test_dsi.py
imports: import numpy
  from numpy.testing import assert_equal, assert_almost_equal, assert_raises
  from dipy.data import get_fnames, dsi_voxels, default_sphere
  from dipy.reconst.dsi import DiffusionSpectrumModel
  from dipy.reconst.odf import gfa
  from dipy.direction.peaks import peak_directions
  from dipy.sims.voxel import sticks_and_ball
  from dipy.core.gradients import gradient_table
  from dipy.core.subdivide_octahedron import create_unit_sphere
  from dipy.core.sphere_stats import angular_similarity
label_desc: Use image node_id 2 for calling a global function with example usage: test_multivox_dsi() without return types