etag property
etag is used for optimistic concurrency control as a way to help prevent simultaneous updates of a instance configuration from overwriting each other.
It is strongly suggested that systems make use of the etag in the read-modify-write cycle to perform instance configuration updates in order to avoid race conditions: An etag is returned in the response which contains instance configurations, and systems are expected to put that etag in the request to update instance configuration to ensure that their change is applied to the same version of the instance configuration. If no etag is provided in the call to update the instance configuration, then the existing instance configuration is overwritten blindly.
Implementation
core.String? etag;