{"ast_node_type":"import","tokens":[{"end":102,"kind":"keyword","start":0,"text":"//"}]}
                // NB: we double the key index, so that we can later use *2 to get the back references
                // NB: the source/target are switched here too
                &mut edge_pairs.iter().map(|&(_, tgt)| N::new(tgt.index() + num_nodes)),