code: def test_discard_issue(self):
      # https://github.com/networkx/networkx/issues/2071
      g = nx.DiGraph()
      g.add_edges_from(
          [
              ("b0", "b1"),
              ("b1", "b2"),
              ("b2", "b3"),
              ("b3", "b1"),
              ("b1", "b5"),
              ("b5", "b6"),
              ("b5", "b8"),
              ("b6", "b7"),
              ("b8", "b7"),
              ("b7", "b3"),
              ("b3", "b4"),
          ]
      )
      df = nx.dominance_frontiers(g, "b0")
      assert df == {
          "b4": set(),
          "b5": {"b3"},
          "b6": {"b7"},
          "b7": {"b3"},
          "b0": set(),
          "b1": {"b1"},
          "b2": {"b3"},
          "b3": {"b1"},
          "b8": {"b7"},
      }
  
imports: import pytest
  import networkx
label_desc: Use image node_id 10 for calling the TestDominanceFrontiers obj's underlying member method code with example usage: obj.test_discard_issue() without return types