I have some questions about the new DefinedNamespace:

1. Can we restore a non-private API to get the URI of the namespace itself? Something like the uri() method on the now-deprecated ClosedNamespace:

rdflib.OWL.uri()   # "http://www.w3.org/2002/07/owl#"

2. I couldn't find a documented way to get the complete set of URIs within a DefinedNamespace. It appears necessary to do something like this:

from rdflib import OWL, URIRef
owl_uris: Set[URIRef] = {OWL[str(x)] for x in OWL.__annotations__}  # this can be generalized to a function

It would be nice to have the above functionality implemented as, say, a method (on DefinedNamespaceMeta?). On ClosedNamespace, it looks like it was possible to get this result via dir(OWL), since __dir__ was defined on that class.