Returns a Bokeh glyph object.

def _init_glyph(self, plot, mapping, properties):
        """
        Returns a Bokeh glyph object.
        """
        properties.pop('legend', None)
        for prop in ['color', 'alpha']:
            if prop not in properties:
                continue
            pval = properties.pop(prop)
            line_prop = 'line_%s' % prop
            fill_prop = 'fill_%s' % prop
            if line_prop not in properties:
                properties[line_prop] = pval
            if fill_prop not in properties and fill_prop in self.style_opts:
                properties[fill_prop] = pval
        properties = mpl_to_bokeh(properties)
        plot_method = self._plot_methods['single']
        glyph = plot_method(**dict(properties, **mapping))
        plot.add_layout(glyph)
        return None, glyph