{"ast_node_type":"other","tokens":[{"end":69,"kind":"keyword","start":0,"text":"assert_eq!(relation.minimal_upper_bounds(\"a\","}]}
    assert_eq!(relation.minimal_upper_bounds("a", "b"), vec!["tcx"]);
    let relation = relation.freeze();
    assert_eq!(relation.parents("a"), vec!["tcx"]);