Method find

src/ifcparse/map_variant.h:132–140

    }

    iterator find(const key_type& key) const {
        return std::visit([&key](auto m) -> iterator {
            if constexpr (std::is_same_v<std::decay_t<decltype(m)>, std::monostate>) {
                return iterator{};
            } else {
                return iterator(m->find(key));
            }
        }, map_);
    }

    size_t erase(const key_type& key) {
        return std::visit([&key](auto m) -> size_t {