Add missing Pyre mode headers] [shard:2/N]

Differential Revision: D68767682

fbshipit-source-id: 493fb06271d2b9cfdaffff60b211ceeeeb948f8b

Author: generatedunixname89002005307016

torchtnt/utils/nan.py

@@ -4,6 +4,8 @@
 # This source code is licensed under the BSD-style license found in the
 # LICENSE file in the root directory of this source tree.
 
+# pyre-strict
+
 from collections import deque
 from typing import Callable, Iterator, List, Optional, Sequence, Union