fingerprint

Specifies a fingerprint for this resource, which is essentially a hash of the metadata's contents and used for optimistic locking. The fingerprint is initially generated by Compute Engine and changes after every request to modify or update metadata. You must always provide an up-to-date fingerprint hash in order to update or change metadata, otherwise the request will fail with error 412 conditionNotMet. To see the latest fingerprint, make get() request to the firewall policy.