std::unordered_map<int, std::unordered_map<int, std::unique_ptr<deviceTypeX>>> deviceTypeXMap;

template <typename classType>
void addInstance(std::unordered_map<int, std::unordered_map<int, std::unique_ptr<classType>>> &outer,
                             int outerKey, std::unique_ptr<classType> instanceToAdd, int innerKey) {
    auto outerSearch = outer.find(outerKey);
    if (outerSearch != outer.end()) {
        outerSearch->second.try_emplace(innerKey, std::move(instanceToAdd));
    }
    else{ //outer key not found }
}

addInstance(deviceTypeXMap, desc.idVendor, std::make_unique<specificDevice>(dev, ctx), desc.idProduct);