code: def _cell_attribute_append(self, selection, tab, attributes):
          
  
          cell_attributes = self.code_array.cell_attributes
  
          thick_bottom_cells = []
          thick_right_cells = []
  
          # Does any cell in selection.cells have a larger bottom border?
  
          if "borderwidth_bottom" in attributes:
              bwidth = attributes["borderwidth_bottom"]
              for row, col in selection.cells:
                  __bwidth = cell_attributes[row, col, tab]["borderwidth_bottom"]
                  if __bwidth > bwidth:
                      thick_bottom_cells.append((row, col))
  
          # Does any cell in selection.cells have a larger right border?
          if "borderwidth_right" in attributes:
              rwidth = attributes["borderwidth_right"]
              for row, col in selection.cells:
                  __rwidth = cell_attributes[row, col, tab]["borderwidth_right"]
                  if __rwidth > rwidth:
                      thick_right_cells.append((row, col))
  
          for thick_cell in thick_bottom_cells + thick_right_cells:
              try:
                  selection.cells.remove(thick_cell)
              except ValueError:
                  pass
  
          cell_attributes.append((selection, tab, attributes))
  
          if thick_bottom_cells:
              bsel = copy(selection)
              bsel.cells = thick_bottom_cells
              battrs = copy(attributes)
              battrs.pop("borderwidth_bottom")
              cell_attributes.append((bsel, tab, battrs))
  
          if thick_right_cells:
              rsel = copy(selection)
              rsel.cells = thick_right_cells
              rattrs = copy(attributes)
              rattrs.pop("borderwidth_right")
              cell_attributes.append((rsel, tab, rattrs))
docs: Appends to cell_attributes with checks