docs: public Waiter<GetUserRequest> userExists() {
  
          return new WaiterBuilder<GetUserRequest, GetUserResult>().withSdkFunction(new GetUserFunction(client))
                  .withAcceptors(new HttpSuccessStatusAcceptor(WaiterState.SUCCESS), new UserExists.IsNoSuchEntityMatcher())
                  .withDefaultPollingStrategy(new PollingStrategy(new MaxAttemptsRetryStrategy(20), new FixedDelayStrategy(1)))
                  .withExecutorService(executorService).build();
      }