code: def setUp(self):
      self.pdag_mix = PDAG(
          directed_ebunch=[("A", "C"), ("D", "C")],
          undirected_ebunch=[("B", "A"), ("B", "D")],
      )
      self.pdag_dir = PDAG(
          directed_ebunch=[
              ("A", "B"),
              ("D", "B"),
              ("A", "C"),
              ("D", "C"),
          ]
      )
      self.pdag_undir = PDAG(
          undirected_ebunch=[
              ("A", "C"),
              ("D", "C"),
              ("B", "A"),
              ("B", "D"),
          ]
      )
      self.pdag_latent = PDAG(
          directed_ebunch=[("A", "C"), ("D", "C")],
          undirected_ebunch=[("B", "A"), ("B", "D")],
          latents=["A", "D"],
      )
  
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 TestPDAG obj's underlying member method code with example usage: obj.setUp() without return types