The change token from a previous fetch operation.
- iOS 10.0+
- macOS 10.12+
- Mac Catalyst 13.0+
- tvOS 10.0+
- watchOS 3.0+
Assign the token you received previously from the
fetch to this property. Doing so yields only the changes that have occurred since your last fetch operation. If you specify
nil for this parameter, the operation starts fetching changes at the beginning.