MetadataRepository can't be implemented

I am unable to extend the MetadataRepository class as shown in the Teiid documentation. Per rareddy_mk-kafka the class is now abstract (public abstract class MetadataRepository<F,C>) and can't be implemented through the service loader. I'd like to see if you could implement a mechanism that allows custom metadata repositories again.

Ref: https://developer.jboss.org/thread/278855