code: def test_multivoxel():
      """Test fitting with multivoxel data.
  
      We generate a multivoxel signal to test the fitting for multivoxel data.
      This is to ensure that the fitting routine takes care of signals packed as
      1D, 2D or 3D arrays.
      """
      ivim_fit_multi = ivim_model_trr.fit(data_multi)
  
      est_signal = ivim_fit_multi.predict(gtab, S0=1.0)
      assert_array_equal(est_signal.shape, data_multi.shape)
      assert_array_almost_equal(
          ivim_fit_multi.model_params, ivim_params_trr
      )
      assert_array_almost_equal(est_signal, data_multi)
  
imports: import warnings
  import numpy
  from numpy.testing import assert_array_equal, assert_array_almost_equal, assert_raises, assert_array_less, assert_, assert_equal
  from dipy.testing import assert_greater_equal
  import pytest
  from dipy.reconst.ivim import ivim_prediction, IvimModel
  from dipy.core.gradients import gradient_table, generate_bvecs
  from dipy.sims.voxel import multi_tensor
  from dipy.utils.optpkg import optional_package
label_desc: Use image node_id 4 for calling a global function with example usage: test_multivoxel() without return types