code: def _update_plot(self, key, element, bars, lims, ranges):
          
          main = self.adjoined.main
          _, y1 = element.range(1)
          offset = self.offset * y1
          range_item, main_range, dim = get_sideplot_ranges(self, element, main, ranges)
  
          # Check if plot is colormapped
          plot_type = Store.registry['matplotlib'].get(type(range_item))
          if isinstance(plot_type, PlotSelector):
              plot_type = plot_type.get_plot_class(range_item)
          opts = self.lookup_options(range_item, 'plot')
          if plot_type and issubclass(plot_type, ColorbarPlot):
              cidx = opts.options.get('color_index', None)
              if cidx is None:
                  opts = self.lookup_options(range_item, 'style')
                  cidx = opts.kwargs.get('color', None)
                  if cidx not in range_item:
                      cidx = None
              cdim = None if cidx is None else range_item.get_dimension(cidx)
          else:
              cdim = None
  
          # Get colormapping options
          if isinstance(range_item, (HeatMap, Raster)) or cdim:
              style = self.lookup_options(range_item, 'style')[self.cyclic_index]
              cmap = cm.get_cmap(style.get('cmap'))
              main_range = style.get('clims', main_range)
          else:
              cmap = None
  
          if offset and ('offset_line' not in self.handles):
              self.handles['offset_line'] = self.offset_linefn(offset,
                                                               linewidth=1.0,
                                                               color='k')
          elif offset:
              self._update_separator(offset)
  
          if cmap is not None:
              self._colorize_bars(cmap, bars, element, main_range, dim)
          return bars
docs: Process the bars and draw the offset line as necessary. If a
          color map is set in the style of the 'main' ViewableElement object, color
          the bars appropriately, respecting the required normalization
          settings.