src/PHPDish/Bundle/PostBundle/Service/BookManager.php
public function findBook($slug)
    {
        $category = $this->categoryManager->findCategoryBySlug($slug);
        if (!$category || !$category->isBook()) {
            throw new \InvalidArgumentException('The book is not exists');
        }
        return $category;
    }
public function findBook($slug)
    {
        $category = $this->categoryManager->findCategoryBySlug($slug);
        if (!$category || !$category->isBook()) {
            throw new \InvalidArgumentException('The book is not exists');
        }
        return $category;
    }
{@inheritdoc}