code: def test_add_multiple_nodes(self):
      self.graph.add_nodes_from([("a", "b"), ("b", "c")])
      self.assertListEqual(
          hf.recursive_sorted(self.graph.nodes()),
          [["a", "b"], ["b", "c"]],
      )
  
imports: import unittest
  import numpy
  from pgmpy.factors.discrete import DiscreteFactor
  from pgmpy.models import JunctionTree
  from pgmpy.tests import help_functions
label_desc: Use image node_id 4 for calling the TestJunctionTreeCreation obj's underlying member method code with example usage: obj.test_add_multiple_nodes() without return types