def METHOD_NAME(self, request, user, form, cleaned_data):
    for field in self.get_fields():
        if field.fieldname not in cleaned_data:
            continue
        try:
            cleaned_data[field.fieldname] = field.clean(
                request, user, cleaned_data[field.fieldname]
            )
        except ValidationError as e:
            form.add_error(field.fieldname, e)
    return cleaned_data