code: def render_to_string(self, request, template, context, content_instance=None):
          
          if not content_instance:
              content_instance = PluginContext(request)
  
          content_instance.update(context)
          return render_to_string(template, content_instance.flatten(), request=request)
docs: Render a custom template with the :class:`~PluginContext` as context instance.