protected function _translationFields()
    {
        $fields = $this->getConfig('fields');

        if ($fields) {
            return $fields;
        }

        $table = $this->_translationTable();
        $fields = $table->getSchema()->columns();
        $fields = array_values(array_diff($fields, ['id', 'locale']));

        $this->setConfig('fields', $fields);

        return $fields;
    }