LSH matching save and load

Hi; I'm using LSH for binary descriptor matching In order to save the processing time ; I would to perform the training step at once and save the index in a file for the next query. How can do that ? Should I use the save/load of the FlannBasedMatcher class ? How ? cv::Ptr indexParams = new cv::flann::LshIndexParams(20, 10, 2); FlannBasedMatcher matcher(indexParams);