code: def unmerge(self, unmerge_area, tab):
          
  
          top, left, bottom, right = unmerge_area
          selection = Selection([(top, left)], [(bottom, right)], [], [], [])
          attr = {"merge_area": None, "locked": False}
  
          self._set_cell_attr(selection, tab, attr)
docs: Unmerges all cells in unmerge_area