code: def make_fake_signal():
      hemisphere = hemi_icosahedron.subdivide(2)
      bvecs = np.concatenate(([[0, 0, 0]], hemisphere.vertices))
      bvals = np.zeros(len(bvecs)) + 2000
      bvals[0] = 0
      gtab = gradient_table(bvals, bvecs)
  
      evals = np.array([[2.1, 0.2, 0.2], [0.2, 2.1, 0.2]]) * 10**-3
      evecs0 = np.eye(3)
      evecs1 = evecs0
      a = evecs0[0]
      b = evecs1[1]
      S1 = single_tensor(gtab, 0.55, evals[0], evecs0)
      S2 = single_tensor(gtab, 0.45, evals[1], evecs1)
      return S1 + S2, gtab, np.vstack([a, b])
  
imports: import warnings
  import numpy
  import numpy.linalg
  import numpy.testing
  from dipy.testing import assert_true
  from numpy.testing import assert_array_equal, assert_array_almost_equal, assert_equal, assert_raises
  from scipy.special import sph_harm
  from dipy.core.sphere import hemi_icosahedron, Sphere
  from dipy.core.gradients import gradient_table
  from dipy.core.interpolation import NearestNeighborInterpolator
  from dipy.sims.voxel import single_tensor
  from dipy.direction.peaks import peak_directions
  from dipy.reconst.shm import sf_to_sh, sh_to_sf
  from dipy.sims.voxel import multi_tensor_odf
  from dipy.data import mrtrix_spherical_functions
  from dipy.reconst import odf
  from dipy.reconst.shm import real_sh_descoteaux_from_index, real_sym_sh_basis, real_sym_sh_mrtrix, real_sh_descoteaux, real_sh_tournier, sph_harm_ind_list, order_from_ncoef, OpdtModel, normalize_data, hat, lcr_matrix, smooth_pinv, bootstrap_data_array, bootstrap_data_voxel, ResidualBootstrapWrapper, CsaOdfModel, QballModel, SphHarmFit, spherical_harmonics, anisotropic_power, calculate_max_order, sh_to_sf_matrix, gen_dirac, convert_sh_to_full_basis, convert_sh_from_legacy, convert_sh_to_legacy, convert_sh_descoteaux_tournier, descoteaux07_legacy_msg, tournier07_legacy_msg
label_desc: Use image node_id 13 for calling a global function with example usage: make_fake_signal() and returns: unknown,  gtab,  np