code: def test_add_variables(self):
      self.model.add_variables(["x4"], [3], [0.1, 0.2, 0.4])
      np_test.assert_array_equal(
          self.model.variables, np.array(["x1", "x2", "x3", "x4"])
      )
      np_test.assert_array_equal(
          self.model.cardinality, np.array([2, 3, 2, 3])
      )
      self.assertListEqual(
          self.model.inhibitor_probability,
          [[0.6, 0.4], [0.2, 0.4, 0.7], [0.1, 0.4], [0.1, 0.2, 0.4]],
      )
  
      self.model.add_variables(
          ["x5", "x6"], [3, 2], [[0.1, 0.2, 0.4], [0.5, 0.5]]
      )
      np_test.assert_array_equal(
          self.model.variables,
          np.array(["x1", "x2", "x3", "x4", "x5", "x6"]),
      )
      np_test.assert_array_equal(
          self.model.cardinality, np.array([2, 3, 2, 3, 3, 2])
      )
      self.assertListEqual(
          self.model.inhibitor_probability,
          [
              [0.6, 0.4],
              [0.2, 0.4, 0.7],
              [0.1, 0.4],
              [0.1, 0.2, 0.4],
              [0.1, 0.2, 0.4],
              [0.5, 0.5],
          ],
      )
  
file_path: pgmpy/pgmpy/tests/test_models/test_NoisyOrModels.py
imports: import unittest
  import numpy
  import numpy.testing
  from pgmpy.models import NoisyOrModel
label_desc: Use image node_id 2 for calling the TestNoisyOrModelMethods obj's underlying member method code with example usage: obj.test_add_variables() without return types