code: def test_tree_all_pairs_lca_routine_bails_on_DAGs(self):
      G = nx.DiGraph([(3, 4), (5, 4)])
      pytest.raises(nx.NetworkXError, list, tree_all_pairs_lca(G))
  
imports: from itertools import chain, combinations, product
  import pytest
  import networkx
label_desc: Use image node_id 13 for calling the TestTreeLCA obj's underlying member method code with example usage: obj.test_tree_all_pairs_lca_routine_bails_on_DAGs() without return types