code: def test_check_model(self):
      self.model.add_cpds(self.cpd1, self.cpd2, self.cpd3)
      self.assertEqual(self.model.check_model(), True)
  
      self.model.add_edge("x1", "x4")
      cpd4 = LinearGaussianCPD("x4", [4, -1], 3, ["x2"])
      self.model.add_cpds(cpd4)
  
      self.assertRaises(ValueError, self.model.check_model)
  
file_path: pgmpy/pgmpy/tests/test_models/test_LinearGaussianBayesianNetwork.py
imports: import unittest
  import numpy
  import numpy.testing
  from pgmpy.factors.continuous import LinearGaussianCPD
  from pgmpy.factors.discrete import TabularCPD
  from pgmpy.models import LinearGaussianBayesianNetwork
label_desc: Use image node_id 5 for calling the TestLGBNMethods obj's underlying member method code with example usage: obj.test_check_model() without return types