code: def test_const_fail_cases(self):
      G1 = nx.DiGraph(
          [
              (0, 1),
              (2, 1),
              (10, 0),
              (10, 3),
              (10, 4),
              (5, 10),
              (10, 6),
              (1, 4),
              (5, 3),
          ]
      )
      G2 = nx.DiGraph(
          [
              ("a", "b"),
              ("c", "b"),
              ("k", "a"),
              ("k", "d"),
              ("k", "e"),
              ("f", "k"),
              ("k", "g"),
              ("b", "e"),
              ("f", "d"),
          ]
      )
      gparams = _GraphParameters(G1, G2, None, None, None, None, None)
      sparams = _StateParameters(
          {0: "a", 1: "b", 2: "c", 3: "d"},
          {"a": 0, "b": 1, "c": 2, "d": 3},
          None,
          None,
          None,
          None,
          None,
          None,
          None,
          None,
      )
      u, v = 10, "k"
      assert _consistent_PT(u, v, gparams, sparams)
  
      # Delete one uncovered neighbor of u. Notice how it still passes the
      # test. Two reasons for this:
      #   1. If u, v had different degrees from the beginning, they wouldn't
      #      be selected as candidates in the first place.
      #   2. Even if they are selected, consistency is basically
      #      1-look-ahead, meaning that we take into consideration the
      #      relation of the candidates with their mapped neighbors.
      #      The node we deleted is not a covered neighbor.
      #      Such nodes will be checked by the cut_PT function, which is
      #      basically the 2-look-ahead, checking the relation of the
      #      candidates with T1, T2 (in which belongs the node we just deleted).
      G1.remove_node(6)
      assert _consistent_PT(u, v, gparams, sparams)
  
      # Add one more covered neighbor of u in G1
      G1.add_edge(u, 2)
      assert not _consistent_PT(u, v, gparams, sparams)
  
      # Compensate in G2
      G2.add_edge(v, "c")
      assert _consistent_PT(u, v, gparams, sparams)
  
      # Add one more covered neighbor of v in G2
      G2.add_edge(v, "x")
      G1.add_node(7)
      sparams.mapping.update({7: "x"})
      sparams.reverse_mapping.update({"x": 7})
      assert not _consistent_PT(u, v, gparams, sparams)
  
      # Compensate in G1
      G1.add_edge(u, 7)
      assert _consistent_PT(u, v, gparams, sparams)
  
imports: import itertools
  import pytest
  import networkx
  from networkx import vf2pp_is_isomorphic, vf2pp_isomorphism
  from networkx.algorithms.isomorphism.vf2pp import _consistent_PT, _cut_PT, _feasibility, _find_candidates, _find_candidates_Di, _GraphParameters, _initialize_parameters, _matching_order, _restore_Tinout, _restore_Tinout_Di, _StateParameters, _update_Tinout
label_desc: Use image node_id 4 for calling the TestDiGraphISOFeasibility obj's underlying member method code with example usage: obj.test_const_fail_cases() without return types