public function deleteTranslation($key, $language = null) {
		if($language === null) {
			$languages = $this->getLanguageList();
		}
		else {
			$languages = array($language);
		}
		foreach ($languages as $language) {
			$messageFile = $this->getMessageFile($language);
			$messageFile->deleteMessage($key);
			$messageFile->save();
			
			unset($this->messages[$language][$key]);
		}
	}