public static function get_image_sizes() {
		// Bailout early if cached image configuration is available.
		if ( self::$sizes ) {
			return self::$sizes;
		}

		/**
		 * Filters image sizes used in Timmy.
		 *
		 * @since 0.13.0
		 *
		 * @param array $sizes Image configuration array. Default array().
		 */
		$sizes = apply_filters( 'timmy/sizes', array() );

		/**
		 * Fallback for get_image_sizes() function
		 *
		 * TODO: deprecate in 1.0.0
		 */
		if ( empty( $sizes ) && function_exists( 'get_image_sizes' ) ) {
			$sizes = get_image_sizes();
		}

		// Cache sizes for next requests.
		self::$sizes = $sizes;

		return $sizes;
	}