def _validate_allowed(self, allowed_values, field, value):
        """ {'type': 'list'} """
        if isinstance(value, Iterable) and not isinstance(value, _str_type):
            unallowed = set(value) - set(allowed_values)
            if unallowed:
                self._error(field, errors.UNALLOWED_VALUES, list(unallowed))
        else:
            if value not in allowed_values:
                self._error(field, errors.UNALLOWED_VALUE, value)
{'type': 'list'}