code: def testBackwardSmootherMultiDim(self):
      dlm = builder()
      dlm.add(self.trend1)
      dlm.initialize()
  
      self.kf11.forwardFilter(dlm.model, 1)
      state1 = dlm.model.state
      cov1 = dlm.model.sysVar
  
      self.kf11.forwardFilter(dlm.model, -1)
      self.kf11.backwardSmoother(
          dlm.model, rawState=state1, rawSysVar=cov1
      )
  
      self.assertAlmostEqual(dlm.model.obs[0, 0], 0.0)
  
file_path: pydlm/tests/base/testKalmanFilter.py
imports: import numpy
  import unittest
  from pydlm.modeler.trends import trend
  from pydlm.modeler.seasonality import seasonality
  from pydlm.modeler.builder import builder
  from pydlm.base.kalmanFilter import kalmanFilter
label_desc: Use image node_id 5 for calling the testKalmanFilter obj's underlying member method code with example usage: obj.testBackwardSmootherMultiDim() without return types