The Object API resource representation defines a number of fields as "writable":

• acl[]
• cacheControl
• contentDisposition
• contentEncoding
• contentLanguage
• contentType
• crc32c
• md5Hash
• metadata{}
• name

Key.from_dict currently captures them all in the key's metadata attribute, but that name creates confusion with its metadata key (which stores application-defined key-value pairs).

I think it would be cleaner to map each the non-user-defined fields onto separate attributes, and propagate them to the server via the insert, and patch or update endpoints.

Key should also expose read-only properties for the non-writable resource fields not already mapped, and which aren't constants:

• componentCount
• etag
• generation
• id
• mediaLink
• metageneration
• owner{}
• selfLink
• size
• storageClass
• timeDeleted
• updated