code: def setUp(self):
      self.graph = DAG()
      self.graph.add_edges_from([("diff", "grade"), ("intel", "grade")])
  
imports: import unittest
  import networkx
  import numpy
  import pgmpy.tests.help_functions
  from pgmpy.base import DAG, PDAG
label_desc: Use image node_id 1 for calling the TestDAGMoralization obj's underlying member method code with example usage: obj.setUp() without return types