Method contains

include/pybind11/stl_bind.h:671–677

    size_t len() override { return map.size(); }
    iterator iter() override { return make_key_iterator(map.begin(), map.end()); }
    bool contains(const handle &k) override {
        try {
            return map.find(k.template cast<typename Map::key_type>()) != map.end();
        } catch (const cast_error &) {
            return false;
        }
    }
    Map &map;
};