code: def test_add_sub_3vecs():
      vec1 = np.array([1, 2.3, 3])
      vec2 = np.array([2, 3, 4.3])
      assert_array_almost_equal(vec1 - vec2, pf.sub_3vecs(vec1, vec2))
      assert_array_almost_equal(vec1 + vec2, pf.add_3vecs(vec1, vec2))
      vec2 = [2, -3, 4.3]
      assert_array_almost_equal(vec1 - vec2, pf.sub_3vecs(vec1, vec2))
      assert_array_almost_equal(vec1 + vec2, pf.add_3vecs(vec1, vec2))
  
file_path: dipy/dipy/tracking/tests/test_metrics.py
imports: import numpy
  import numpy.testing
  from numpy.testing import assert_equal, assert_array_almost_equal
  from dipy.tracking import metrics
  from dipy.tracking import distances
  from dipy.utils.deprecator import ExpiredDeprecationError
  from dipy.testing.decorators import set_random_number_generator
label_desc: Use image node_id 6 for calling a global function with example usage: test_add_sub_3vecs() without return types