QBankApi.php
public function categories()
    {
        if (!$this->categories instanceof CategoriesController) {
            $this->categories = new CategoriesController($this->getClient(), $this->cachePolicy, $this->cache);
            $this->categories->setLogger($this->logger);
        }

        return $this->categories;
    }
public function categories()
    {
        if (!$this->categories instanceof CategoriesController) {
            $this->categories = new CategoriesController($this->getClient(), $this->cachePolicy, $this->cache);
            $this->categories->setLogger($this->logger);
        }

        return $this->categories;
    }
Categories defines which PropertySets should be available for Media. All Media belongs to exactly one Category.

@return CategoriesController