lookup_combined.json

{
    "nodes": [
        {"name": "foo", "group": 1, "index": 0},
        {"name": "bar", "group": 2, "index": 1},
        {"name": "baz", "group": 2, "index": 2},
        {"name": "foobar", "group": 3, "index": 3}
    ],
    "links": [
        {"source": 0, "target": 0},
        {"source": 1, "target": 1},
        {"source": 2, "target": 2},
        {"source": 3, "target": 3},
        {"source": 1, "target": 3},
        {"source": 2, "target": 3}
    ]
}