code: public PubsubFuture<Void> acknowledge(final String canonicalSubscriptionName, final List<String> ackIds) {
      final String path = canonicalSubscriptionName + ":acknowledge";
      final AcknowledgeRequest req = AcknowledgeRequest.builder()
          .ackIds(ackIds)
          .build();
      return post("acknowledge", path, req, VOID);
    }
docs: Acknowledge a batch of received messages.
  
  @param canonicalSubscriptionName The canonical (including project name) subscription to acknowledge messages on.
  @param ackIds                    List of message ID's to acknowledge.
  @return A future that is completed when this request is completed.