code: def highlight_current_cell(self):
          
          if self.cell_separators is None or \
            not self.highlight_current_cell_enabled:
              return
          cursor, whole_file_selected, whole_screen_selected =\
              self.select_current_cell_in_visible_portion()
          selection = TextDecoration(cursor)
          selection.format.setProperty(QTextFormat.FullWidthSelection,
                                       to_qvariant(True))
          selection.format.setBackground(self.currentcell_color)
  
          if whole_file_selected:
              self.clear_extra_selections('current_cell')
          elif whole_screen_selected:
              if self.has_cell_separators:
                  self.set_extra_selections('current_cell', [selection])
                  self.update_extra_selections()
              else:
                  self.clear_extra_selections('current_cell')
          else:
              self.set_extra_selections('current_cell', [selection])
              self.update_extra_selections()
docs: Highlight current cell