def _postprocess_hover(self, renderer, source):
        """
        Attaches renderer to hover tool and processes tooltips to
        ensure datetime data is displayed correctly.
        """
        hover = self.handles.get('hover')
        if hover is None:
            return
        if hover.renderers == 'auto':
            hover.renderers = []
        hover.renderers.append(renderer)

        # If datetime column is in the data replace hover formatter
        for k, v in source.data.items():
            if k+'_dt_strings' in source.data:
                tooltips = []
                for name, formatter in hover.tooltips:
                    if formatter == '@{%s}' % k:
                        formatter = '@{%s_dt_strings}' % k
                    tooltips.append((name, formatter))
                hover.tooltips = tooltips
Attaches renderer to hover tool and processes tooltips to
        ensure datetime data is displayed correctly.