{
  "version": "0.1",
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      "op": {"type": "Cube", "size": {"x": 40, "y": 40, "z": 80}}
    },
    "2": {
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      "name": "outer_translated",
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    },
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    },
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      "name": "hollow_tube",
      "op": {"type": "Difference", "left": 2, "right": 4}
    }
  },
  "materials": {},
  "part_materials": {},
  "roots": [{"root": 5, "material": "default"}]
}