protected function get_messages()
    {
        $lang_file = __DIR__.DIRECTORY_SEPARATOR.'lang'.DIRECTORY_SEPARATOR.$this->lang.'.php';
        $messages = require $lang_file;

        if ($validation_methods_errors = self::$validation_methods_errors) {
            $messages = array_merge($messages, $validation_methods_errors);
        }
        return $messages;
    }