protected function _getSecondRule() {
        $relation = $this->getRelation();
        $firstRule = $relation->name;
        $hasCustomRelName = $this->_hasCustomRelName();
        $modelIds = $this->_getModelIdsAlphabetically();

        if ($hasCustomRelName) {
            return $modelIds[0];
        }

        return $modelIds[0] !== $firstRule
            ? $modelIds[0]
            : $modelIds[1]
        ;
    }