{"ast_node_type":"other","tokens":[{"end":47,"kind":"keyword","start":0,"text":"pre_order_to_real.push(graph.start_node());"}]}
    pre_order_to_real.push(graph.start_node());
        IndexVec::from_elem_n(None, graph.num_nodes());
    parent.push(PreorderIndex::ZERO); // the parent of the root node is the root for now.