public function getPossibleVariationsForProduct(Product $product)
 {
     $attributes = $product->getAttributes();
     $this->createQueryBuilder($alias);
 }
 /**
  * 
  * @param EntityManager $em
  * @param Product $product
  * @return ArrayCollection
  */
 public static function generate(EntityManager $em, Product $product)
 {
     $productAttributes = $product->getAttributes();
     $_instance = new self($em, $product);
     return $_instance->factoryByProductAttributes($productAttributes);
 }