code: def _register_external_service(self, plugin_name, plugin_instance):
          
          for attr in plugin_instance.get_external_services().keys():
              if attr in self._external_services:
                  raise PluginException("External service with name {} already exists! Unable to add "
                                        "services from plugin {}.".format(attr, plugin_name))
              self._external_services[attr] = plugin_instance.get_external_services().get(attr)
docs: Register an external service.
  
          :param plugin_name: Service name
          :param plugin_instance: PluginBase
          :return: