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