Don't include __slots__ in dir().

Author: ashleysommer

rdflib/namespace/__init__.py

@@ -226,6 +226,7 @@ def __repr__(self) -> str:
 # considered part of __dir__ results. These should be all annotations on
 # `DefinedNamespaceMeta`.
 _DFNS_RESERVED_ATTRS: Set[str] = {
+ "__slots__",
  "_NS",
  "_warn",
  "_fail",