code: def update_test_data(self):
      data = [
          dict(
              state=gs.zeros(2),
              prior_values=gs.eye(2),
              process_values=gs.eye(1),
              obs_values=2.0 * gs.eye(1),
              observation=gs.array([0.6]),
              expected_state=gs.array([0.2, 0.0]),
              expected_cov=from_vector_to_diagonal_matrix(
                  gs.array([2.0 / 3.0, 1.0])
              ),
          )
      ]
      return self.generate_tests(data)
  
imports: import geomstats.backend
  from geomstats.algebra_utils import from_vector_to_diagonal_matrix
  from geomstats.test.data import TestData
label_desc: Use image node_id 2 for calling the KalmanFilterTestData obj's underlying member method code with example usage: obj.update_test_data() and returns: self