public function printStudentsAndClasses()
    {
        $qb = $this->createQueryBuilder('students')
            ->innerJoin('students.classes', 'classes')
            ->getQuery();

        $iterator = function (ClassEntity $classEntity): string {
            return $classEntity->getName();
        };

        /** @var Student $student */
        foreach ($qb->getResult() as $student) {
            echo $student->getName() . ' Classes: ' . \implode(', ', $student->getClasses()->map($iterator)->toArray());
        }
    }