code: def test_all_pairs_lca_issue_4574(self):
      G = nx.DiGraph()
      G.add_nodes_from(range(17))
      G.add_edges_from(
          [
              (2, 0),
              (1, 2),
              (3, 2),
              (5, 2),
              (8, 2),
              (11, 2),
              (4, 5),
              (6, 5),
              (7, 8),
              (10, 8),
              (13, 11),
              (14, 11),
              (15, 11),
              (9, 10),
              (12, 13),
              (16, 15),
          ]
      )
  
      assert nx.lowest_common_ancestor(G, 7, 9) == None
  
imports: from itertools import chain, combinations, product
  import pytest
  import networkx
label_desc: Use image node_id 15 for calling the TestDAGLCA obj's underlying member method code with example usage: obj.test_all_pairs_lca_issue_4574() without return types