code: def test_reduce(self):
      phi = self.phi1.reduce([("x1", 7)], inplace=False)
      self.assertEqual(phi.variables, ["x2", "x3"])
      np_test.assert_array_equal(
          phi.mean, np.asarray([[0], [1]], dtype=float)
      )
      np_test.assert_array_equal(
          phi.covariance, np.asarray([[4, -4], [-4, 7]], dtype=float)
      )
      self.assertEqual(phi._precision_matrix, None)
  
      phi = self.phi1.reduce([("x1", 3), ("x2", 1)], inplace=False)
      self.assertEqual(phi.variables, ["x3"])
      np_test.assert_array_equal(phi.mean, np.array([[0]], dtype=float))
      np_test.assert_array_equal(
          phi.covariance, np.asarray([[3]], dtype=float)
      )
      self.assertEqual(phi._precision_matrix, None)
  
      self.phi1.reduce([("x1", 7)])
      self.assertEqual(self.phi1.variables, ["x2", "x3"])
      np_test.assert_array_equal(
          self.phi1.mean, np.asarray([[0], [1]], dtype=float)
      )
      np_test.assert_array_equal(
          self.phi1.covariance,
          np.asarray([[4, -4], [-4, 7]], dtype=float),
      )
      self.assertEqual(self.phi1._precision_matrix, None)
  
      self.phi1 = self.phi3.copy()
      self.phi1.reduce([("x1", 3), ("x2", 1)])
      self.assertEqual(self.phi1.variables, ["x3"])
      np_test.assert_array_equal(
          self.phi1.mean, np.asarray([[0]], dtype=float)
      )
      np_test.assert_array_equal(
          self.phi1.covariance, np.asarray([[3]], dtype=float)
      )
      self.assertEqual(self.phi1._precision_matrix, None)
  
      self.phi1 = self.phi3.copy()
      self.phi1.reduce([("x2", 1), ("x1", 3)])
      self.assertEqual(self.phi1.variables, ["x3"])
      np_test.assert_array_equal(
          self.phi1.mean, np.asarray([[0]], dtype=float)
      )
      np_test.assert_array_equal(
          self.phi1.covariance, np.asarray([[3]], dtype=float)
      )
      self.assertEqual(self.phi1._precision_matrix, None)
  
imports: import unittest
  import numpy
  import numpy.testing
  from pgmpy.factors.distributions import GaussianDistribution
label_desc: Use image node_id 6 for calling the TestJGDMethods obj's underlying member method code with example usage: obj.test_reduce() without return types