code: def test_apparent_kurtosis_coef():
      """Apparent kurtosis coefficients are tested for a spherical kurtosis
      tensor"""
  
      sph = Sphere(xyz=gtab.bvecs[gtab.bvals > 0])
      AKC = dki.apparent_kurtosis_coef(params_sph, sph)
  
      # check all direction
      for d in range(len(gtab.bvecs[gtab.bvals > 0])):
          assert_array_almost_equal(AKC[d], Kref_sphere)
  
imports: import numpy
  import random
  import dipy.reconst.dki
  import dipy.reconst.dti
  from numpy.testing import assert_array_almost_equal, assert_array_equal, assert_almost_equal, assert_raises
  from dipy.sims.voxel import multi_tensor_dki
  from dipy.io.gradients import read_bvals_bvecs
  from dipy.core.gradients import gradient_table
  from dipy.data import get_fnames
  from dipy.reconst.dti import from_lower_triangular, decompose_tensor
  from dipy.reconst.dki import mean_kurtosis, carlson_rf, carlson_rd, axial_kurtosis, radial_kurtosis, mean_kurtosis_tensor, _positive_evals, lower_triangular, kurtosis_fractional_anisotropy
  from dipy.core.sphere import Sphere
  from dipy.data import default_sphere
  from dipy.core.geometry import sphere2cart
  from dipy.utils.optpkg import optional_package
  from dipy.utils.tripwire import TripWireError
label_desc: Use image node_id 6 for calling a global function with example usage: test_apparent_kurtosis_coef() without return types