Method equal_range

common/unordered_inline_set.h:519–523

        return find(x) != end();
    }
    std::pair<iterator, iterator> equal_range( const Key& key ) {
        auto it = find(key);
        if (it == end()) return {it, it};
        return {it, it.get_next()};
    }
    std::pair<const_iterator, const_iterator> equal_range( const Key& key ) const {
        auto it = find(key);
        if (it == end()) return {it, it};