docs: public ZMatrixRMaj getQ(ZMatrixRMaj Q ) {
          Q = UtilDecompositons_ZDRM.checkIdentity(Q,N,N);
  
          Arrays.fill(u,0,N*2,0);
          for( int j = N-2; j >= 0; j-- ) {
              QrHelperFunctions_ZDRM.extractHouseholderColumn(QH,j+1,N,j,u,0);
              QrHelperFunctions_ZDRM.rank1UpdateMultR(Q, u, 0,gammas[j], j + 1, j + 1, N, b);
          }
  
          return Q;
      }