code: def testGetMSE(self):
      self.dlm1.stableMode(False)
      self.dlm1.fitForwardFilter()
      mse1 = self.dlm1.getMSE()
      mse_expect = 0
      for i in range(20):
          mse_expect += (
              self.dlm1.result.predictedObs[i] - self.data[i]
          ) ** 2
      mse_expect /= 20
      self.assertAlmostEqual(mse1, mse_expect)
  
      self.dlm2.stableMode(False)
      self.dlm2.fitForwardFilter()
      self.dlm2.result.filteredSteps = (0, 19)
      mse2 = self.dlm2.getMSE()
      mse_expect = 2.0 / 20
  
      self.assertAlmostEqual(mse2, mse_expect)
  
imports: import numpy
  import unittest
  from pydlm.modeler.trends import trend
  from pydlm.modeler.seasonality import seasonality
  from pydlm.modeler.dynamic import dynamic
  from pydlm.modeler.autoReg import autoReg
  from pydlm.dlm import dlm
label_desc: Use image node_id 25 for calling the testDlm obj's underlying member method code with example usage: obj.testGetMSE() without return types