Current type of field.properties.fields is `any[][]` -- I believe it should instead be `any[]` per the example in the API docs:

```
{
      "ref": "a_group_field_ref",
      "title": "group field",
      "type": "group",
      "properties": {
        "description": "Question group description",
        "show_button": true,
        "button_text": "Some text",
        "fields": [
          {
            "ref": "nice_readable_website_reference",
            "title": "website",
            "type": "website",
            "properties": {
              "description": "Cool description for the website"
            }
          }
        ]
      },
```

https://developer.typeform.com/create/reference/create-form/

Note, that the actual docs above the example specify the type of `Field.properties.fields` as `array of arrays` but I believe this is an error -- the shape of object above is what I see when in the actual JSON of my form when exported from Typeform.