[NFC] polish ./colossalai/amp/torch_amp/__init__.py code style
diff --git a/colossalai/amp/torch_amp/__init__.py b/colossalai/amp/torch_amp/__init__.py
index 8943b86d6aaf..893cc890d68e 100644
--- a/colossalai/amp/torch_amp/__init__.py
+++ b/colossalai/amp/torch_amp/__init__.py
@@ -1,9 +1,12 @@
+from typing import Optional
+
 import torch.nn as nn
-from torch.optim import Optimizer
 from torch.nn.modules.loss import _Loss
+from torch.optim import Optimizer
+
 from colossalai.context import Config
-from .torch_amp import TorchAMPOptimizer, TorchAMPModel, TorchAMPLoss
-from typing import Optional
+
+from .torch_amp import TorchAMPLoss, TorchAMPModel, TorchAMPOptimizer
 
 
 def convert_to_torch_amp(model: nn.Module,
