code: def _css_helper(self):
          
          entries = [entry for entry in self._plugin_manager.call_hook("css") if entry is not None]
          # Load javascript for the current page
          entries += self._get_ctx()["css"]
          entries = ["<link href='" + entry + "' rel='stylesheet'>" for entry in entries]
          return "\n".join(entries)
docs: Add CSS links for the current page and for the plugins