TypeVar can not be used in issubclass

spinn_utilities/overrides.py

@@ -133,8 +133,8 @@ def __is_similar_type(self, method_type, super_type, arg):
             return True
 
         # If one is generic they must be the exact same object
-        if (isinstance(method_type, _BaseGenericAlias) or
-                isinstance(super_type, _BaseGenericAlias)):
+        if (isinstance(method_type, (TypeVar, _BaseGenericAlias)) or
+                isinstance(super_type, (TypeVar, _BaseGenericAlias))):
             if arg == "return":
                 if self._return_narrowing:
                     return True
@@ -172,8 +172,11 @@ def __is_similar_type(self, method_type, super_type, arg):
                     f"Method {self._override_name} has {arg} typed as "
                     f"{method_type} while super is typed as {super_type}. "
                     f"For None imported types they must be exactly the same")
-
-        return issubclass(method_type, super_type)
+        try:
+            return issubclass(method_type, super_type)
+        except TypeError as ex:
+            raise TypeError (f"Unable to subtype {super_type}"
+                             f" {type(super_type)} for {arg}") from ex
 
     def __verify_method_types(self, method: Method):
         try: