json_schema: {
      "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"
  }