public function getLangFallbacks( $lang ) {
		if ( self::$fallbackCache === null ) {
			// Lazy-initialize
			self::$fallbackCache = $this->fetchLangFallbacks();
		}

		$lang = $this->normalizeLang( $lang );
		return isset( self::$fallbackCache[$lang] ) ? self::$fallbackCache[$lang] : [ 'en' ];
	}