code: def _collapse_ranges(ranges, ja):
      
      arow0, _, acol0, acol1 = ranges[ja]
      jb = 0
      while jb < len(ranges):
          if jb == ja:
              jb += 1
              continue
          brow0, brow1, bcol0, bcol1 = ranges[jb]
          if bcol0 <= acol1 and brow1 >= arow0 and \
                  not(bcol0 == acol1 and brow1 == arow0):
              ranges[ja][0] = arow0 = min(arow0, brow0)
              ranges[ja][3] = acol1 = max(acol1, bcol1)
              del ranges[jb]
              if jb < ja:
                  ja -= 1
          else:
              jb += 1
      return ja
docs: Within the `ranges` list find those 2d-ranges that overlap with `ranges[ja]`
      and merge them into `ranges[ja]`. Finally, return the new index of the
      ja-th range within the `ranges` list.