mpyw\Co\Internal\CoOption::validateBool PHP Метод

    private static function validateBool($key, $value)
    {
        $value = filter_var($value, FILTER_VALIDATE_BOOLEAN, ['flags' => FILTER_NULL_ON_FAILURE]);
        if ($value === null) {
            throw new \InvalidArgumentException("Option[{$key}] must be boolean.");
        }
        return $value;
    }