[NFC] polish colossalai/nn/layer/utils/common.py code style (#983)

colossalai/nn/layer/utils/common.py

@@ -13,7 +13,8 @@ from torch import Tensor, nn
 
 
 class CheckpointModule(nn.Module):
-    def __init__(self, checkpoint: bool = True, offload : bool = False):
+
+    def __init__(self, checkpoint: bool = True, offload: bool = False):
         super().__init__()
         self.checkpoint = checkpoint
         self._use_checkpoint = checkpoint
@@ -78,6 +79,7 @@ def get_tensor_parallel_mode():
 
 
 def _ntuple(n):
+
     def parse(x):
         if isinstance(x, collections.abc.Iterable):
             return x