code: def test_class_init_without_data(self):
      self.assertIsInstance(self.G, nx.DiGraph)
  
imports: import unittest
  import networkx
  import pandas
  import numpy
  from pgmpy.models import NaiveBayes
  from pgmpy.independencies import Independencies
label_desc: Use image node_id 2 for calling the TestBaseModelCreation obj's underlying member method code with example usage: obj.test_class_init_without_data() without return types