{
    "num_parts": 2,
    "unique_part_ids": [
        14,
        15
    ],
    "motion_hierarchy": [
        [
            14,
            15
        ]
    ],
    "joints": [
        {
            "part_id": 14,
            "type": "fixed"
        },
        {
            "part_id": 15,
            "type": "revolute"
        }
    ]
}