C   dynamic array cleared when object returned
template <typename T>
Bag<T> Bag<T>::operator+ (const Bag<T>& bag) {
    int sizeofCurrentMultiset = cardinality_;
    int sizeofPassedMultiset  = bag.cardinality_;
    int totalSize = sizeofCurrentMultiset + sizeofPassedMultiset;

    Bag<T> newBag(totalSize);

    for (int i = 0; i < sizeofCurrentMultiset; i++) {
        newBag.insert(array_[i]);
    }

    for (int i = 0; i < sizeofPassedMultiset; i++) {
        newBag.insert(bag.array_[i]);
    }

    return newBag;
}