{"ast_node_type":"other","tokens":[{"end":82,"kind":"keyword","start":0,"text":"assert_eq!(d.immediate_dominator(0),"}]}
    assert_eq!(d.immediate_dominator(0), None); // <-- note that 0 is not in graph
    let d = dominators(&graph);
    assert_eq!(d.immediate_dominator(1), Some(6));