fix prov graph literal type value property

Author: fmigneault

mypy-stubs/rdflib/graph.pyi

@@ -16,7 +16,7 @@ from rdflib import query
 from rdflib.collection import Collection
 from rdflib.paths import Path
 from rdflib.resource import Resource
-from rdflib.term import BNode, Identifier, Node
+from rdflib.term import BNode, Identifier, Literal, Node
 
 class Graph(Node):
     base: Any = ...
@@ -66,7 +66,7 @@ class Graph(Node):
     ) -> Iterable[Node]: ...
     def objects(
         self, subject: Optional[Any] = ..., predicate: Optional[Any] = ...
-    ) -> Iterable[Identifier]: ...
+    ) -> Iterable[Union[Identifier, Literal]]: ...
     def subject_predicates(self, object: Optional[Any] = ...) -> None: ...
     def subject_objects(self, predicate: Optional[Any] = ...) -> None: ...
     def predicate_objects(self, subject: Optional[Any] = ...) -> None: ...

tests/test_provenance.py

@@ -573,7 +573,7 @@ def check_prov(
     else:
         account_names = set(g.objects(account, FOAF.accountName))
         assert len(account_names) == 1
-        account_name = account_names.pop()
+        account_name = cast(Literal, account_names.pop())
         machine_user = provenance._whoami()[0]
         assert account_name.value == machine_user