code: def testAlter(self):
      dlm4 = dlm(self.data)
      dlm4 + self.trend1 + dynamic(features=self.features, discount=1)
      dlm4.fitForwardFilter()
      # the filtered step range should be (0, 19)
      self.assertEqual(dlm4.result.filteredSteps, [0, 19])
  
      dlm4.alter(date=15, data=1, component="main")
      self.assertEqual(dlm4.result.filteredSteps, [0, 14])
      dlm4.fitForwardFilter()
  
      newData = [0] * 9 + [1] + [0] * 10
      newData[15] = 1
      dlm5 = dlm(newData)
      dlm5 + self.trend1 + dynamic(features=self.features, discount=1)
      dlm5.fitForwardFilter()
  
      # The two chain should have the same filtered obs
      self.assertAlmostEqual(
          np.sum(
              np.array(dlm4.result.filteredObs)
              - np.array(dlm5.result.filteredObs)
          ),
          0.0,
      )
  
      # test alter the feature
      dlm4.alter(date=0, data=[1, 1], component="dynamic")
      self.assertAlmostEqual(
          dlm4.builder.dynamicComponents["dynamic"].features[0], [1, 1]
      )
  
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 9 for calling the testDlm obj's underlying member method code with example usage: obj.testAlter() without return types