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.

def _update_plot(self, key, element, bars, lims, ranges):
        """
        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.
        """
        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