static BufferedImage gridLOLToImage(LL<Int> lol, L<Int> cellWidths, L<Int> cellHeights) {
  L<Matrix<Int>> lom = mapWithIndex(lol,
    (i, m) -> listToMatrix(cellWidths.get(i), m));
  
  MatrixOfMatrices<Int> mom = listToMatrix_cols(cols, lom);

  BufferedImage restored = newBufferedImage(image.getWidth(), image.getHeight());
  L<Int> cellX1s = partialSums_firstIs0(cellWidths);
  L<Int> cellY1s = partialSums_firstIs0(cellHeights);
  forEachWithPosition(mom, (x, y, cell) ->
    drawIntMatrix(restored, cell, cellX1s.get(x), cellY1s.get(y)));
  ret restored;
}