code: def test_class_init_without_data(self):
      self.assertIsInstance(self.graph, FactorGraph)
  
imports: import numpy
  import unittest
  from pgmpy.factors.discrete import DiscreteFactor
  from pgmpy.models import FactorGraph
  from pgmpy.models import MarkovNetwork
  from pgmpy.models import JunctionTree
  from pgmpy.tests import help_functions
label_desc: Use image node_id 2 for calling the TestFactorGraphCreation obj's underlying member method code with example usage: obj.test_class_init_without_data() without return types