public function check(BasketInterface $basket)
 {
     $balls = $basket->getBalls();
     // more balls in basket than required
     if ($balls->count() > $this->balls->count()) {
         return false;
     }
     return !array_diff(iterator_to_array($balls), iterator_to_array($this->balls));
 }
 public function check(BasketInterface $basket)
 {
     $balls = $basket->getBalls();
     $diff = array_diff(iterator_to_array($balls), iterator_to_array($this->balls));
     return count($diff) == $balls->count() - 1;
 }