code: def test_add_single_edge_without_timeslice(self):
      self.assertRaises(ValueError, self.network.add_edge, "a", "b")
  
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 11 for calling the TestDynamicBayesianNetworkCreation obj's underlying member method code with example usage: obj.test_add_single_edge_without_timeslice() without return types