code: def bracket_test_data(self):
      smoke_data = [
          dict(
              mat_a=gs.array([[1.0, 2.0], [3.0, 4.0]]),
              mat_b=gs.array([[1.0, 2.0], [3.0, 4.0]]),
              expected=gs.array([[0.0, 0.0], [0.0, 0.0]]),
          ),
          dict(
              mat_a=gs.array(
                  [[[1.0, 2.0], [3.0, 4.0]], [[1.0, 2.0], [0.0, 1.0]]]
              ),
              mat_b=gs.array(
                  [[[2.0, 4.0], [5.0, 4.0]], [[1.0, 4.0], [5.0, 4.0]]]
              ),
              expected=gs.array(
                  [
                      [[-2.0, -8.0], [9.0, 2.0]],
                      [[10.0, 6.0], [0.0, -10.0]],
                  ]
              ),
          ),
      ]
      return self.generate_tests(smoke_data)
  
imports: import math
  import geomstats.backend
  from geomstats.test.data import TestData
  from .base import MatrixVectorSpaceTestData
  from .riemannian_metric import RiemannianMetricTestData
label_desc: Use image node_id 2 for calling the MatrixOperationsSmokeTestData obj's underlying member method code with example usage: obj.bracket_test_data() and returns: self