docs: public DMatrixRMaj getQ(DMatrixRMaj Q ) {
          Q = UtilDecompositons_DDRM.checkIdentity(Q,N,N);
  
          for( int j = N-2; j >= 0; j-- ) {
              u[j+1] = 1;
              for( int i = j+2; i < N; i++ ) {
                  u[i] = QH.get(i,j);
              }
              QrHelperFunctions_DDRM.rank1UpdateMultR(Q, u, gammas[j], j + 1, j + 1, N, b);
          }
  
          return Q;
      }