code: def test_moralize_disconnected(self):
      graph_copy = self.graph.copy()
      graph_copy.add_node("disconnected")
      moral_graph = graph_copy.moralize()
      self.assertListEqual(
          hf.recursive_sorted(moral_graph.edges()),
          [["diff", "grade"], ["diff", "intel"], ["grade", "intel"]],
      )
      self.assertEqual(
          sorted(moral_graph.nodes()),
          ["diff", "disconnected", "grade", "intel"],
      )
  
imports: import unittest
  import networkx
  import numpy
  import pgmpy.tests.help_functions
  from pgmpy.base import DAG, PDAG
label_desc: Use image node_id 4 for calling the TestDAGMoralization obj's underlying member method code with example usage: obj.test_moralize_disconnected() without return types