{
    "properties": {
        "attributes": {
            "properties": {
                "option1": {
                    "enum": [
                        "val1",
                        "val2"
                    ],
                    "title": "option1",
                    "type": "string"
                },
                "option2": {
                    "title": "option2",
                    "type": "integer"
                },
                "option3": {
                    "items": {
                        "type": "string"
                    },
                    "title": "option3",
                    "type": "array"
                }
            },
            "title": "feature attributes",
            "type": "object"
        }
    },
    "title": "Union",
    "type": "object"
}