public function belongsToMany($alias, $class, $junction, $foreignKey = null, $relatedKey = null, Closure $conditions = null) {
        $relation = (new ManyToMany($alias, $class))
            ->setJunction($junction)
            ->setPrimaryForeignKey($foreignKey)
            ->setRelatedForeignKey($relatedKey);

        if ($conditions) {
            $relation->setConditions($conditions);
        }

        return $this->addRelation($relation);
    }