docs: public NearestNeighborsResults knn(int index, int k) throws Exception {
          NearestNeighborRequest request = new NearestNeighborRequest();
          request.setInputIndex(index);
          request.setK(k);
          HttpRequestWithBody req = Unirest.post(url + "/knn");
          req.header("accept", "application/json")
                  .header("Content-Type", "application/json").body(request);
          addAuthHeader(req);
  
          NearestNeighborsResults ret = req.asObject(NearestNeighborsResults.class).getBody();
          return ret;
      }