{
    "event": "Missing notation in node",
    "mainVariation": [
        "e4",
        "e5",
        {
            "notation": "Nf3",
            "variations": [
                [ "Nc3" ],
                [
                    "f4",
                    "exf4",
                    "Bc4",
                    { "comment": "I'm a comment..." }
                ]
            ]
        }
    ]
}