code: def test_rotation_mat2vec():
      r = rotation_mat2vec(np.diag([-1, 1, -1]))
      assert not np.isnan(r).max()
  
file_path: nipy/nipy/algorithms/registration/tests/test_affine.py
imports: import numpy
  import pytest
  from numpy.testing import assert_array_almost_equal, assert_array_equal
  from ....testing import assert_almost_equal
  from ..affine import Affine, Affine2D, Rigid, Rigid2D, Similarity, Similarity2D, rotation_mat2vec, slices2aff, subgrid_affine
label_desc: Use image node_id 3 for calling a global function with example usage: test_rotation_mat2vec() without return types