{"ast_node_type":"other","tokens":[{"end":55,"kind":"keyword","start":0,"text":"IndexVec::from_elem_n(None,"}]}
        IndexVec::from_elem_n(None, graph.num_nodes());
    let mut real_to_pre_order: IndexVec<G::Node, Option<PreorderIndex>> =
    pre_order_to_real.push(graph.start_node());