code: def test_realign4d_descending():
      runs = [IM, IM]
      R = FmriRealign4d(runs, tr=3, slice_order="descending")
      assert_array_equal(R.slice_times, (2, 1, 0))
      assert R.tr == 3
  
imports: import warnings
  import nibabel
  import numpy
  import pytest
  from nibabel import io_orientation
  from numpy.testing import assert_array_almost_equal, assert_array_equal
  from ....None import load_image
  from ....core.image.image_spaces import make_xyz_image, xyz_affine
  from ....io.nibcompat import get_header
  from ....testing import funcfile
  from ...slicetiming.timefuncs import st_02413, st_42031, st_43210
  from ..affine import Rigid
  from ..groupwise_registration import FmriRealign4d, Image4d, Realign4d, Realign4dAlgorithm, SpaceRealign, SpaceTimeRealign, make_grid, resample4d
label_desc: Use image node_id 7 for calling a global function with example usage: test_realign4d_descending() without return types