docs: def formgroup_factory(form_classes,
                        formgroup=None,
                        state_validators=None,
                        ):
      """Return a FormGroup class for the given form[set] form_classes.
  
      """
  
      base_class = formgroup or FormGroup
      if state_validators is not None:
          base_class = StateValidatorFormGroup
  
      if not issubclass(base_class, FormGroup):
          raise TypeError("Base formgroup class must subclass FormGroup.")
  
      return type(
          'FormGroup',
          (base_class,),
          dict(
              form_classes=form_classes,
              state_validators=state_validators,
          ),
      )