code: public ApiSuccessResponse sendCustomNotification(String id, CustomNotificationData customNotificationData) throws ApiException {
          ApiResponse<ApiSuccessResponse> resp = sendCustomNotificationWithHttpInfo(id, customNotificationData);
          return resp.getData();
      }
docs: Send a custom notification
  Send a custom notification to the specified chat. The notification is typically used as a trigger for some custom behavior on the recipient&#39;s end.
  @param id The ID of the chat interaction. (required)
  @param customNotificationData Request parameters. (optional)
  @return ApiSuccessResponse
  @throws ApiException If fail to call the API, e.g. server error or cannot deserialize the response body