code: def test_add_edge_nonstring(self):
      self.graph.add_edge(1, 2)
  
imports: from pgmpy.base import UndirectedGraph
  from pgmpy.tests import help_functions
  import unittest
label_desc: Use image node_id 11 for calling the TestUndirectedGraphCreation obj's underlying member method code with example usage: obj.test_add_edge_nonstring() without return types