def existing(self):
        """ find existing content assigned to this layout"""
        catalog = api.portal.get_tool('portal_catalog')
        results = []
        layout_path = self._get_layout_path(
            self.request.form.get('layout', '')
        )
        for brain in catalog(layout=layout_path):
            results.append({
                'title': brain.Title,
                'url': brain.getURL()
            })
        return json.dumps({
            'total': len(results),
            'data': results
        })
find existing content assigned to this layout