Method insert

src/fl/stl/set.h:433–435

    void clear() { mTree.clear(); }
    
    fl::pair<const_iterator, bool> insert(const Key& key) {
        return mTree.insert(key);
    }
    
    fl::pair<const_iterator, bool> insert(Key&& key) {
        return mTree.insert(fl::move(key));