etag property
ETag is the store's entity tag for the bytes currently at this key, with the quotes the store wraps it in stripped. It is an opaque VERSION and not a checksum to verify against: a single-part upload's tag happens to be the MD5 of the content and a multipart upload's is not, and nothing here says which this was. Compare two reads of one key to learn whether the object changed; absent for a folder entry, and for an object the store reports none for.
Please note: This property should have been non-nullable! Since the specification file does not include a default value (using the "default:" property), however, the generated source code must fall back to having a nullable type. Consider adding a "default:" property in the specification file to hide this note.
Implementation
String? etag;