code: def test_str(self):
      cpd1 = LinearGaussianCPD("x", [0.23], 0.56)
      cpd2 = LinearGaussianCPD(
          "y", [0.67, 1, 4.56, 8], 2, ["x1", "x2", "x3"]
      )
      self.assertEqual(cpd1.__str__(), "P(x) = N(0.23; 0.56)")
      self.assertEqual(
          cpd2.__str__(),
          "P(y | x1, x2, x3) = N(1*x1 + " "4.56*x2 + 8*x3 + 0.67; 2)",
      )
  
file_path: pgmpy/pgmpy/tests/test_factors/test_continuous/test_Linear_Gaussian_CPD.py
imports: import unittest
  import numpy.testing
  import pandas
  import numpy
  from pgmpy.factors.continuous import LinearGaussianCPD
label_desc: Use image node_id 5 for calling the TestLGCPD obj's underlying member method code with example usage: obj.test_str() without return types