code: def test_normalize(self):
      def pdf2(x1, x2):
          return 2 * self.pdf2(x1, x2)
  
      phi2 = CustomDistribution(["x1", "x2"], pdf2)
      phi4 = phi2.copy()
  
      phi4.normalize()
      self.assertEqual(phi4.variables, phi2.variables)
      for inp in np.random.rand(1, 2):
          np_test.assert_almost_equal(
              phi4._pdf(inp[0], inp[1]), self.pdf2(inp[0], inp[1])
          )
  
      phi4 = phi2.normalize(inplace=False)
      self.assertEqual(phi4.variables, phi4.variables)
      for inp in np.random.rand(1, 2):
          np_test.assert_almost_equal(
              phi4._pdf(inp[0], inp[1]), self.pdf2(inp[0], inp[1])
          )
  
imports: import unittest
  import numpy
  import numpy.testing
  from scipy.special import beta
  from scipy.stats import multivariate_normal
  from pgmpy.factors.distributions import CustomDistribution
label_desc: Use image node_id 12 for calling the TestCustomDistributionMethods obj's underlying member method code with example usage: obj.test_normalize() and returns: unknown