code: protected function getFindBySubjectAndSupplierQuery()
      {
          if (null !== $this->findBySubjectAndSupplierQuery) {
              return $this->findBySubjectAndSupplierQuery;
          }
  
          $qb = $this->createFindBySubjectQueryBuilder();
  
          return $this->findBySubjectAndSupplierQuery = $qb
              ->andWhere($qb->expr()->eq($this->getAlias() . '.supplier', ':supplier'))
              ->getQuery();
      }
docs: Returns the "find by subject and supplier" query.
  
  @return \Doctrine\ORM\Query