    {
              "args": [
                {
                  "coins-inserted": [],
                  "coins-returned": [],
                  "dispensed": null,
                  "inventory": { "a1": { "name": "taco", "qty": 10, "price": 0.85 } },
                  "err-msg": null
                },
                "quarter"
              ],
              "parent": "root",
              "return": {
                "coins-inserted": ["quarter"],
                "coins-returned": [],
                "disp