Method find

src/fl/stl/multi_set.h:292–299

    }

    iterator find(const Key& key) {
        ValueWithId search_key(key, 0);
        auto it = mTree.lower_bound(search_key);
        if (it != mTree.end() && it->value == key) {
            return iterator(it);
        }
        return end();
    }

    const_iterator find(const Key& key) const {
        ValueWithId search_key(key, 0);