code: def test_sphere_find_closest():
      sphere1 = unit_octahedron.subdivide(4)
      for ii in range(sphere1.vertices.shape[0]):
          nt.assert_equal(
              sphere1.find_closest(sphere1.vertices[ii]), ii
          )
  
imports: import numpy
  import numpy.testing
  import pytest
  import warnings
  from dipy.core.sphere import Sphere, HemiSphere, unique_edges, unique_sets, faces_from_sphere_vertices, disperse_charges, fibonacci_sphere, disperse_charges_alt, _get_forces, _get_forces_alt, unit_octahedron, unit_icosahedron, hemi_icosahedron
  from dipy.core.geometry import cart2sphere, vector_norm
  from dipy.core.sphere_stats import random_uniform_on_sphere
  from dipy.utils.optpkg import optional_package
label_desc: Use image node_id 13 for calling a global function with example usage: test_sphere_find_closest() without return types