public function createMissingValueSet(Content $content)
    {
        if ($content->getContentType() !== null && $content->getValueSet() === null)
        {
            $valueSet = new ValueSet();
            $this->em->persist($valueSet);

            $valueSet->setSchema($content->getContentType()->getSchema());
            $content->setValueSet($valueSet);

            $content = $this->save($content);
        }

        return $content;
    }