# fwd to "lo"
[
    {
        "fwd": "lo"
    }
]

# fwd to mark map { 0x00000001 : "lo", 0x00000002 : "lo"}
[
    {
        "fwd": {
            "map": {
                "left": {
                    "meta": "mark"
                },
                "right": {
                    "set": [
                        [
                            "0x00000001",
                            "lo"
                        ],
                        [
                            "0x00000002",
                            "lo"
                        ]
                    ]
                }
            }
        }
    }
]