remove allow-untyped-defs from onnx/_internal/_lazy_import.py (pytorch#143943)

Pull Request resolved: pytorch#143943
Approved by: https://github.com/justinchuby

Author: bobrenjc93

torch/onnx/_internal/_lazy_import.py

@@ -1,6 +1,5 @@
 """Utility to lazily import modules."""
 
-# mypy: allow-untyped-defs
 from __future__ import annotations
 
 import importlib
@@ -17,7 +16,7 @@ def __init__(self, module_name: str) -> None:
     def __repr__(self) -> str:
         return f"<lazy module '{self._name}'>"
 
-    def __getattr__(self, attr):
+    def __getattr__(self, attr: str) -> object:
         if self._module is None:
             self._module = importlib.import_module(".", self._name)
         return getattr(self._module, attr)