code: def test_retraction(self, tangent_vec, base_point, expected, atol):
      res = self.space.metric.retraction(tangent_vec, base_point)
      self.assertAllClose(res, expected, atol=atol)
  
imports: import pytest
  import geomstats.backend
  from geomstats.geometry.grassmannian import Grassmannian
  from geomstats.test.test_case import TestCase
  from geomstats.test.vectorization import generate_vectorization_data
  from geomstats.test_cases.geometry.base import LevelSetTestCase
  from geomstats.test_cases.geometry.riemannian_metric import RiemannianMetricTestCase
label_desc: Use image node_id 1 for calling the StiefelCanonicalMetricTestCase obj's underlying member method code with example usage: obj.test_retraction(tangent_vec, base_point, expected, atol) without return types