docs: def _grow_to(self, width, height, top_tc=None):
          """
          Grow this cell to *width* grid columns and *height* rows by expanding
          horizontal spans and creating continuation cells to form vertical
          spans.
          """
          def vMerge_val(top_tc):
              if top_tc is not self:
                  return ST_Merge.CONTINUE
              if height == 1:
                  return None
              return ST_Merge.RESTART
  
          top_tc = self if top_tc is None else top_tc
          self._span_to_width(width, top_tc, vMerge_val(top_tc))
          if height > 1:
              self._tc_below._grow_to(width, height-1, top_tc)