code: def test_all_pairs_lca_nonexisting_pairs_exception(self):
      pytest.raises(nx.NodeNotFound, all_pairs_lca, self.DG, [(-1, -1)])
  
imports: from itertools import chain, combinations, product
  import pytest
  import networkx
label_desc: Use image node_id 7 for calling the TestDAGLCA obj's underlying member method code with example usage: obj.test_all_pairs_lca_nonexisting_pairs_exception() without return types