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* Field groups in forms. There is a new string `group` member on `Field` that is used to group, a `group` namespace on `Form` you can use to set attrs, tag, etc. Global styling for form groups is done via the `FieldGroup` class. The bootstrap style has been updated to support this feature out of the box.
* Validation could be bypassed for forms if they have been saved via `form.refine_done()`. This became the default behavior for `.as_view()` in iommi 4.1 so that release is broken.