Returns a Bokeh glyph object.

def _init_glyph(self, plot, mapping, properties):
        """
        Returns a Bokeh glyph object.
        """
        properties = mpl_to_bokeh(properties)
        plot_method = self._plot_methods.get('batched' if self.batched else 'single')
        if isinstance(plot_method, tuple):
            # Handle alternative plot method for flipped axes
            plot_method = plot_method[int(self.invert_axes)]
        renderer = getattr(plot, plot_method)(**dict(properties, **mapping))
        return renderer, renderer.glyph