code: def test_add_self_loop_raises_error(self):
      self.assertRaises(ValueError, self.graph.add_edge, "a", "a")
  
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 8 for calling the TestFactorGraphCreation obj's underlying member method code with example usage: obj.test_add_self_loop_raises_error() without return types