I was following a hash table implementation tutorial and came across this:

class HashTable {
private:
    static const int hashGroups = 10;
    std::list<std::pair<int,std::string>> table[hashGroups];

bool HashTable::isEmpty() const {
    int sum{};
    for(int i{}; i < hashGroups; i++) {
        sum += table[i].size();
    }
    
    if(!sum) {
        return true;
    }
    return false;
}

In the isEmpty() member function, why is table[i].size() valid? In my interpretation, table is a list of pairs, therefore, table[i] should return a pair at index [i]. However, there are no member function size() in std::pair.