public function getResolvedConcreteFlag($abstract)
    {
        if (!$this->hasResolvedConcrete($abstract)) {
            throw Internal\Exception\ReflectionExceptionFactory::invalidArgument(
                sprintf(
                    "Parameter 1 of %s must be an abstract class name which exists in resolved concrete stack.",
                     __METHOD__
                )
            );
        }

        return explode('|', $this->resolved[$abstract]['flag']);
    }