, keylines, descriptors, returnFloatDescr);             plhs[0] = MxArray(descriptors);             if (nlhs > 0)                 plhs[0] = toStruct(keylines);         }         else if (rhs[0].isCell()) { // second variant that accepts an image set             //vector<Mat> images(rhs[0].toVector<Mat>());             vector<Mat> images