code: def add_highlight(self, artist, *args, **kwargs):
          
          hl = _pick_info.make_highlight(
              artist, *args,
              **ChainMap({"highlight_kwargs": self.highlight_kwargs}, kwargs))
          if hl:
              artist.axes.add_artist(hl)
              return hl
docs: Create, add, and return a highlighting artist.
  
          This method is should be called with an "unpacked" `Selection`,
          possibly with some fields set to None.
  
          It is up to the caller to register the artist with the proper
          `Selection` (by calling ``sel.extras.append`` on the result of this
          method) in order to ensure cleanup upon deselection.