Fix lint error

Author: kunlunl

megatron/core/transformer/attention.py

@@ -57,7 +57,9 @@
     rearrange = None
 
 try:
-    from flash_attn_3.flash_attn_interface import _flash_attn_forward
+    from flash_attn_3.flash_attn_interface import (
+        _flash_attn_forward,
+    )
     from flash_attn_3.flash_attn_interface import (
         flash_attn_with_kvcache as flash_attn3_with_kvcache,
     )
@@ -68,7 +70,9 @@
 
 if not HAVE_FA3:
     try:
-        from flashattn_hopper.flash_attn_interface import _flash_attn_forward
+        from flashattn_hopper.flash_attn_interface import (
+            _flash_attn_forward,
+        )
         from flashattn_hopper.flash_attn_interface import (
             flash_attn_with_kvcache as flash_attn3_with_kvcache,
         )