template <typename point_t>
class PCLSHRSAdaptor {
public:
    // key_t needed for SHRS , must be defined
    using key_t = size_t;
    using data = pcl::PointCloud<point_t>;
    data const &pcl_ref;
    // the already existing pointcloud is passed
    PCLSHRSAdaptor
    (data const &pcl_ref_) :
        pcl_ref(pcl_ref_) {
    }
    // SHRS works with 2D points, this must return a Vector2d
    inline Vector2d get_point(size_t i_point) const {
        auto const &pnt = pcl_ref.at(i_point);
        return { pnt.x, pnt.y };
    }
    // needed for insert_all() and similar operations
    inline void for_all_keys(std::function<void(key_t)> func) const {
        for(auto i = 0; i < pcl_ref.size(); i++) {
            func(i);
        }
    }
    
    inline bool find_point(size_t i_point) const {
        return i_point < pcl_ref.size();
    }

    inline size_t size() const {
        return pcl_ref.size();
    }
};

using point_t = pcl::PointXYZ;
using shrs_t = SHRS<PCLSHRSAdaptor<point_t>>;
pcl::PointCloud<point_t> test_pcl;
auto const search_radius = .5;
shrs_t shrs_map(PCLSHRSAdaptor<point_t>(test_pcl),
                search_radius);

// fill here the test_pcl ..

// now insert in search data structure
shrs_map.insert_all();

size_t some_index = 11;
shrs_map.insert_point(some_index);
shrs_map.delete_point(some_index);

// must exist in pointcloud
size_t search_point_idx = 7; 
vector<typename shrs_t::key_t> neighbours;
if(shrs_map.find_neighbours(search_point_idx, neighbours) {
    // found neighbour
    for(auto const n_keys : neighbours) {
       auto point_in_radius = test_pcl[n_keys];
       // use the point_in_radius ..
    }
}

Vector2d search_point = { 70., 80. };
vector<typename shrs_t::key_t> neighbours;
if(shrs_map.find_nn_vec(search_point, neighbours)) {
    // found neighbour
    auto nn_index = neighbours.front();
    auto nn_point = test_pcl[nn_index];
    // use the nn_point ..
}