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