Outline use of type_annotation_map to fix mypy issues?

lib/galaxy/model/__init__.py

@@ -206,7 +206,11 @@
 
 _datatypes_registry = None
 
-mapper_registry = registry()
+OPTIONAL_STR_TO_STR_DICT = Optional[Dict[str, str]]
+
+mapper_registry = registry(
+    type_annotation_map={OPTIONAL_STR_TO_STR_DICT: JSONType},
+)
 
 # When constructing filters with in for a fixed set of ids, maximum
 # number of items to place in the IN statement. Different databases
@@ -1404,7 +1408,7 @@ class Job(Base, JobLike, UsesCreateAndUpdateTime, Dictifiable, Serializable):
     params: Mapped[Optional[str]] = mapped_column(TrimmedString(255), index=True)
     handler: Mapped[Optional[str]] = mapped_column(TrimmedString(255), index=True)
     preferred_object_store_id: Mapped[Optional[str]] = mapped_column(String(255), nullable=True)
-    object_store_id_overrides: Mapped[Optional[bytes]] = mapped_column(JSONType)
+    object_store_id_overrides: Mapped[OPTIONAL_STR_TO_STR_DICT] = mapped_column(JSONType)
 
     user = relationship("User")
     galaxy_session = relationship("GalaxySession")

lib/galaxy/model/store/discover.py

@@ -470,8 +470,10 @@ def override_object_store_id(self, output_name: Optional[str] = None) -> Optiona
         if not job:
             return None
         default_object_store_id = job.object_store_id
-        object_store_id_overrides = job.object_store_id_overrides or {}  # type:ignore[var-annotated]
-        return object_store_id_overrides.get(output_name, default_object_store_id)  # type:ignore[union-attr]
+        if not output_name:
+            return default_object_store_id
+        object_store_id_overrides: Dict[str, str] = job.object_store_id_overrides or {}
+        return object_store_id_overrides.get(output_name, default_object_store_id)
 
     @property
     @abc.abstractmethod