WikiClientLibrary currently missesBuiltInDataTypes forWikidata’s lexicographical data.

As far as I can tell, basically three new definitions of the data types, plus a more general implementation ofEntityIdFromJson+EntityIdToJson is needed.

Seemy quick-and-dirty implementation of those (also including a copy-paste of the inaccessibleinternal sealedDelegatePropertyType from the library) which seems to work fine.