public function addMessages(Loader $loader) {
        $loader->setParser($this);

        if ($messages = $loader->load()) {
            foreach ($messages as $locale => $strings) {
                if (!empty($this->_messages[$locale])) {
                    $strings = array_merge($this->_messages[$locale], $strings);
                }

                $this->_messages[$locale] = $strings;
            }
        }

        return $this;
    }