public function operation($operation)
    {
        $existing = $this->operations->findByIdentifier($operation);

        if ($existing) {
            return $existing;
        }

        $scaffoldClass = OperationScaffolder::getClassFromIdentifier($operation);
        if (!$scaffoldClass) {
            throw new InvalidArgumentException(
                sprintf(
                    'Invalid operation: %s added to %s',
                    $operation,
                    $this->getDataObjectClass()
                )
            );
        }
        /**
         * @var OperationScaffolder $scaffolder
         */
        $scaffolder = Injector::inst()->createWithArgs($scaffoldClass, [$this->getDataObjectClass()]);

        $this->operations->push(
            $scaffolder->setChainableParent($this)
        );

        return $scaffolder;
    }