code: def test_init_with_cycle(self):
      self.assertRaises(ValueError, DAG, [("a", "a")])
      self.assertRaises(ValueError, DAG, [("a", "b"), ("b", "a")])
      self.assertRaises(
          ValueError, DAG, [("a", "b"), ("b", "c"), ("c", "a")]
      )
  
imports: import unittest
  import networkx
  import numpy
  import pgmpy.tests.help_functions
  from pgmpy.base import DAG, PDAG
label_desc: Use image node_id 20 for calling the TestDAGCreation obj's underlying member method code with example usage: obj.test_init_with_cycle() without return types