each level needs a weight

hopper_api.json

{
    "url": "http://example.com/api/23/",
    "author": 1,
    "date_created": "2015-03-26T11:01:23.262391Z",
    "date_updated": "2015-03-26T11:01:23.262391Z",
    "html": "<form></form>",
    "javascript": "<script></script>",
    "form": {
        "id": 123,
        "method": "POST",
        "action": "/action/create",
        "enctype": "multipart/form-data",
        "title": "A new form",
        "help_text": "Lorem ipsum.",
        "css_classes": "form inline",
        "elements_css_classes": "form-control",
        "elements": {
            "title": {
                "type": "input",
                "label": "Title",
                "placeholder": "Enter the title",
                "weight": 1,
                "immutable": false,
                "readonly": false,
                "required": true,
                "maxlength": 50,
                "default": ""
            },
            "description": {
                "type": "textarea",
                "label": "Description",
                "placeholder": "Add your description here.",
                "immutable": false,
                "readonly": false,
                "required": false,
                "weight": 2,
                "rows": "10",
                "cols": "50"
            },
            "director": {
                "type": "fieldset",
                "label": "Director",
                "immutable": false,
                "weight": 3,
                "clone": {
                    "extra": 2,
                    "max": 5,
                    "required": 3
                },
                "elements": {
                    "sex": {
                        "type": "radio",
                        "choices": ["female", "male"],
                        "immutable": false,
                        "readonly": false,
                        "required": true,
                        "weight": 3
                    },
                    "first_name": {
                        "type": "input",
                        "placeholder": "",
                        "immutable": false,
                        "readonly": false,
                        "required": true,
                        "weight": 1
                    },
                    "last_name": {
                        "type": "input",
                        "placeholder": "Last name",
                        "immutable": false,
                        "readonly": false,
                        "required": true,
                        "weight": 2
                    },
                    "vegetarian": {
                        "type": "checkbox",
                        "value": "Vegetarian",
                        "immutable": false,
                        "readonly": false,
                        "required": true,
                        "weight": 3,
                        "checked": false
                    }
                }
            }
        }
    }
}