将字符串流推送到优先级队列时出错<stringstream>

问：

std::stringstream makeString(std::string name, std::string number) {
    std::stringstream ss;
    std::string load;
    if(number.size() == 1) {
        ss << "0" << number << " - " << name << std::endl;
    } else {
        ss << number << " - " << name << std::endl;
    }
    return ss;
}

int main(int argc, char const* argv[]) {
    // Write your code here
    std::string inputs;
    std::string priority;
    std::priority_queue<std::stringstream> pqueue;

    while(1 == 1) {

        input("What do you want to do? ", inputs);
        if (inputs == "add") {
            input("Name: ", inputs);
            input("Priority: ", priority);
            std::stringstream ss;
            ss << makeString(inputs, priority).str();
            std::cout << ss.str();
            pqueue.push(ss);
        } else if (inputs == "take") {
            std::stringstream holder;
            holder << pqueue.top().str();
            pqueue.pop();
            std::cout << holder.str() << std::endl;
        } else if (inputs == "end") {
            return 0;
        } else {
            std::cout << inputs << " isn't a valid operation" << std::endl;
        }
    }
}

它应该能够将字符串流推送到优先级队列，但它告诉我它是“对'std：：basic_stringstream'的已删除构造函数的调用”

我该如何解决这个问题？我不能在优先级队列中使用字符串流吗？