code: def test_all_pairs_lca_default_kwarg(self):
      G = nx.DiGraph([(0, 1), (2, 1)])
      sentinel = object()
      assert (
          nx.lowest_common_ancestor(G, 0, 2, default=sentinel)
          is sentinel
      )
  
imports: from itertools import chain, combinations, product
  import pytest
  import networkx
label_desc: Use image node_id 13 for calling the TestDAGLCA obj's underlying member method code with example usage: obj.test_all_pairs_lca_default_kwarg() without return types