public function diff(Collection $collection) : self
    {
        foreach ($this->elements as $element) {
            if (!$collection->contains($element)) {
                $this->removeElement($element);
            }
        }

        foreach ($collection as $element) {
            if (!$this->contains($element)) {
                $this->add($element);
            }
        }

        return $this;
    }