code: def test_mapmri_number_of_coefficients(radial_order=6):
      indices = mapmri_index_matrix(radial_order)
      n_c = indices.shape[0]
      F = radial_order / 2
      n_gt = np.round(1 / 6.0 * (F + 1) * (F + 2) * (4 * F + 3))
      assert_equal(n_c, n_gt)
  
imports: import platform
  import time
  from math import factorial
  from scipy.special import gamma
  import scipy.integrate
  import warnings
  import numpy
  from numpy.testing import assert_almost_equal, assert_array_almost_equal, assert_equal, assert_, assert_raises
  import pytest
  from dipy.core.sphere_stats import angular_similarity
  from dipy.core.subdivide_octahedron import create_unit_sphere
  from dipy.data import get_gtab_taiwan_dsi, default_sphere
  from dipy.direction.peaks import peak_directions
  from dipy.reconst.mapmri import MapmriModel, mapmri_index_matrix
  from dipy.reconst import dti, mapmri
  from dipy.reconst.odf import gfa
  from dipy.reconst.tests.test_dsi import sticks_and_ball_dummies
  from dipy.reconst.shm import sh_to_sf, descoteaux07_legacy_msg
  from dipy.sims.voxel import multi_tensor, multi_tensor_pdf, add_noise, single_tensor, cylinders_and_ball_soderman
  from dipy.testing.decorators import set_random_number_generator
label_desc: Use image node_id 4 for calling a global function with example usage: test_mapmri_number_of_coefficients(radial_order) without return types