code: def get_merging_cell(self, key):
          
  
          row, col, tab = key
  
          # Is cell merged
          merge_area = self[key]["merge_area"]
  
          if merge_area:
              return merge_area[0], merge_area[1], tab
docs: Returns key of cell that merges the cell key
  
          or None if cell key not merged
  
          Parameters
          ----------
          key: 3-tuple of Integer
          \tThe key of the cell that is merged