def METHOD_NAME(self):
    for f in self.forms:
        if f.cleaned_data.get('benefit_class') >= 0:
            params = f.cleaned_data.get('class_parameters')
            benefit = get_benefit_class(f.cleaned_data.get('benefit_class'))(self.instance, params)
            if not params:
                f.cleaned_data['class_parameters'] = {}
                f.instance.class_parameters = {}
                params = {}