code: def test_add_edges_from_nonstring(self):
      self.graph.add_edges_from([(1, 2), (2, 3)])
  
imports: import unittest
  import networkx
  import numpy
  import pgmpy.tests.help_functions
  from pgmpy.base import DAG, PDAG
label_desc: Use image node_id 13 for calling the TestDAGCreation obj's underlying member method code with example usage: obj.test_add_edges_from_nonstring() without return types