code: def test_copy(self):
      copy_phi1 = self.phi1.copy()
      self.assertEqual(copy_phi1.variables, self.phi1.variables)
      np_test.assert_array_equal(copy_phi1.mean, self.phi1.mean)
      np_test.assert_array_equal(
          copy_phi1.covariance, self.phi1.covariance
      )
      np_test.assert_array_equal(
          copy_phi1._precision_matrix, self.phi1._precision_matrix
      )
  
      copy_phi1.marginalize(["x3"])
      self.assertEqual(self.phi1.variables, ["x1", "x2", "x3"])
      np_test.assert_array_equal(
          self.phi1.mean, np.asarray([[1], [-3], [4]], dtype=float)
      )
      np_test.assert_array_equal(
          self.phi1.covariance,
          np.asarray(
              [[4, 2, -2], [2, 5, -5], [-2, -5, 8]], dtype=float
          ),
      )
      self.assertEqual(self.phi1._precision_matrix, None)
  
      self.phi1.marginalize(["x2"])
      self.assertEqual(copy_phi1.variables, ["x1", "x2"])
      np_test.assert_array_equal(
          copy_phi1.mean, np.asarray([[1], [-3]], dtype=float)
      )
      np_test.assert_array_equal(
          copy_phi1.covariance,
          np.asarray([[4, 2], [2, 5]], dtype=float),
      )
      self.assertEqual(copy_phi1._precision_matrix, None)
  
      self.phi1 = self.phi3
  
imports: import unittest
  import numpy
  import numpy.testing
  from pgmpy.factors.distributions import GaussianDistribution
label_desc: Use image node_id 4 for calling the TestJGDMethods obj's underlying member method code with example usage: obj.test_copy() without return types