lineItemNotRemovable example

    public function remove(string $key): void
    {
        $item = $this->get($key);

        if (!$item) {
            throw CartException::lineItemNotFound($key);
        }

        if (!$item->isRemovable()) {
            throw CartException::lineItemNotRemovable($key);
        }

        $this->lineItems->remove($key);
    }

    public function getTransactions(): TransactionCollection
    {
        return $this->transactions;
    }

    public function setTransactions(TransactionCollection $transactions): self
    {