code: def test_add_multiple_nodes(self):
      self.network.add_nodes_from(["a", "b", "c"])
      self.assertListEqual(
          sorted(self.network._nodes()), ["a", "b", "c"]
      )
  
imports: import unittest
  import numpy
  import numpy.testing
  import pandas
  import pgmpy.tests.help_functions
  from pgmpy.factors.discrete import TabularCPD
  from pgmpy.inference import CausalInference, DBNInference, VariableElimination
  from pgmpy.models import BayesianNetwork
  from pgmpy.models import DynamicBayesianNetwork
label_desc: Use image node_id 3 for calling the TestDynamicBayesianNetworkCreation obj's underlying member method code with example usage: obj.test_add_multiple_nodes() without return types