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

  L<Int> cellX1s = partialSums_firstIs0(cellWidths);
  L<Int> cellY1s = partialSums_firstIs0(cellHeights);
  int w = last(cellX1s), h = last(cellY1s);
  BufferedImage restored = newBufferedImage(w, h);
  forEachWithPosition(mom, (x, y, cell) ->
    drawIntMatrix(restored, cell,
      cyclicGet(cellX1s, x),
      cyclicGet(cellY1s, y)));
  ret restored;
}