private const HIGH = 'high';
	private const MEDIUM = 'medium';
	private const LOW = 'low';
	private const NONE = 'none';

	/**
	 * Categories that are configured to be displayed to users
	 *
	 * @return string[]
	 */
	public function getVisibleCategories() {
		return array_merge(
			$this->categories[self::HIGH],
			$this->categories[self::MEDIUM],
			$this->categories[self::LOW]
		);
	}

	/**
	 * Categories that are configured to not be displayed to users
	 *
	 * @return string[]
	 */
	public function getInvisibleCategories() {
		return $this->categories[self::NONE];
	}