      "name": "cartridges[][gear_size]",
            "type": "string",
            "valid_options": [
              "small"
            ]
          },
          {
            "default_value": null,
            "description": "A URL to a downloadable cartridge. You may specify an multiple urls via {'cartridges' : [{'url':'http://...'}, ...]}",
            "name": "cartridges[][url]",
            "type": "string",
            "valid_options": [

            ]
          },
          {
            "default_valu