code: def test_sph_to_cart():
      """Test conversion between sphere and cartesian."""
      # Simple test, expected value (11, 0, 0)
      r, theta, phi = 11.0, 0.0, np.pi / 2.0
      z = r * np.cos(phi)
      rsin_phi = r * np.sin(phi)
      x = rsin_phi * np.cos(theta)
      y = rsin_phi * np.sin(theta)
      coord = _sph_to_cart(np.array([[r, theta, phi]]))[0]
      assert_allclose(coord, (x, y, z), atol=1e-7)
      assert_allclose(coord, (r, 0, 0), atol=1e-7)
      rng = np.random.RandomState(0)
      # round-trip test
      coords = rng.randn(10, 3)
      assert_allclose(
          _sph_to_cart(_cart_to_sph(coords)), coords, atol=1e-5
      )
      # equivalence tests to old versions
      for coord in coords:
          sph = _cart_to_sph(coord[np.newaxis])
          cart = _sph_to_cart(sph)
          sph_old = np.array(_cartesian_to_sphere(*coord))
          cart_old = _sphere_to_cartesian(*sph_old)
          sph_old[1] = np.pi / 2.0 - sph_old[1]  # new convention
          assert_allclose(sph[0], sph_old[[2, 0, 1]], atol=1e-7)
          assert_allclose(cart[0], cart_old, atol=1e-7)
          assert_allclose(cart[0], coord, atol=1e-7)
  
imports: import itertools
  import os
  from pathlib import Path
  import numpy
  import pytest
  from numpy.testing import assert_allclose, assert_almost_equal, assert_array_equal, assert_array_less, assert_equal
  import mne
  from mne import read_trans, write_trans
  from mne.datasets import testing
  from mne.fixes import _get_img_fdata
  from mne.io import read_info
  from mne.transforms import _angle_between_quats, _average_quats, _cart_to_sph, _compute_r2, _euler_to_quat, _find_trans, _find_vector_rotation, _fit_matched_points, _get_trans, _MatchedDisplacementFieldInterpolator, _pol_to_cart, _quat_real, _quat_to_affine, _quat_to_euler, _read_fs_xfm, _sph_to_cart, _topo_to_sph, _validate_pipeline, _write_fs_xfm, apply_trans, combine_transforms, get_ras_to_neuromag_trans, invert_transform, quat_to_rot, rot_to_quat, rotation, rotation3d, rotation3d_align_z_axis, rotation_angles, translation
  from mne.transforms import _SphericalSurfaceWarp
label_desc: Use image node_id 7 for calling a global function with example usage: test_sph_to_cart() without return types