code: @BetaApi
    public final Operation stopInstance(String instance) {
  
      StopInstanceHttpRequest request =
          StopInstanceHttpRequest.newBuilder().setInstance(instance).build();
      return stopInstance(request);
    }
docs: Stops a running instance, shutting it down cleanly, and allows you to restart the instance at a
  later time. Stopped instances do not incur VM usage charges while they are stopped. However,
  resources that the VM is using, such as persistent disks and static IP addresses, will continue
  to be charged until they are deleted. For more information, see Stopping an instance.
  
  <p>Sample code:
  
  <pre><code>
  try (InstanceClient instanceClient = InstanceClient.create()) {
  ProjectZoneInstanceName instance = ProjectZoneInstanceName.of("[PROJECT]", "[ZONE]", "[INSTANCE]");
  Operation response = instanceClient.stopInstance(instance.toString());
  }
  </code></pre>
  
  @param instance Name of the instance resource to stop.
  @throws com.google.api.gax.rpc.ApiException if the remote call fails