Assert\Assertion::isCallable PHP 메소드

    public static function isCallable($value, $message = null, $propertyPath = null)
    {
        if (!is_callable($value)) {
            $message = sprintf($message ?: 'Provided "%s" is not a callable.', static::stringify($value));
            throw static::createException($value, $message, static::INVALID_CALLABLE, $propertyPath);
        }
        return true;
    }