code: def teardown_module():
      global gtab, gtab_2s, crossing_ref, signal_cross
      global multi_params, Kref_sphere, DWI
      global mevals_cross, angles_cross, frac_cross, kt_cross
      global dt_sph, evals_sph, kt_sph, params_sph
      gtab, gtab_2s, crossing_ref, signal_cross = None, None, None, None
      multi_params, Kref_sphere, DWI = None, None, None
      mevals_cross, angles_cross, frac_cross, kt_cross = (
          None,
          None,
          None,
          None,
      )
      dt_sph, evals_sph, kt_sph, params_sph = None, None, None, None
  
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 2 for calling a global function with example usage: teardown_module() without return types