fix typing issue

great_expectations/expectations/expectation.py

@@ -367,6 +367,9 @@ def _register_renderer_functions(cls) -> None:
 
         for candidate_renderer_fn_name in dir(cls):
             attr_obj: Callable | None = getattr(cls, candidate_renderer_fn_name, None)
+            # attrs are not guaranteed to exist https://docs.python.org/3.10/library/functions.html#dir
+            if attr_obj is None:
+                continue
             if not hasattr(attr_obj, "_renderer_type"):
                 continue
             register_renderer(