Returns a Bokeh glyph object.

def _init_glyph(self, plot, mapping, properties):
        """
        Returns a Bokeh glyph object.
        """
        plot_method = properties.pop('plot_method', None)
        properties = mpl_to_bokeh(properties)
        data = dict(properties, **mapping)
        if self._has_holes:
            plot_method = 'multi_polygons'
        elif plot_method is None:
            plot_method = self._plot_methods.get('single')
        renderer = getattr(plot, plot_method)(**data)
        if self.colorbar:
            for k, v in list(self.handles.items()):
                if not k.endswith('color_mapper'):
                    continue
                self._draw_colorbar(plot, v, k[:-12])
        return renderer, renderer.glyph