import Sequence from typing instead of collections.abc

Signed-off-by: ytl0623 <[email protected]>

Author: ytl0623

monai/losses/focal_loss.py

@@ -12,8 +12,7 @@
 from __future__ import annotations
 
 import warnings
-from collections.abc import Sequence
-from typing import Optional
+from typing import Optional, Sequence
 
 import torch
 import torch.nn.functional as F