[format] applied code formatting on changed files in pull request 4021 (#4022)

Co-authored-by: github-actions <github-actions@github.com>

colossalai/nn/layer/base_layer.py

 #!/usr/bin/env python
 # -*- encoding: utf-8 -*-
 
+from contextlib import contextmanager
+
 import torch.nn as nn
 
 from colossalai.context import ParallelMode
 from colossalai.core import global_context as gpc
-from contextlib import contextmanager
 
 
 class ParallelLayer(nn.Module):

tests/test_device/test_device_mesh.py

-from colossalai.device.device_mesh import DeviceMesh
 import torch
 
+from colossalai.device.device_mesh import DeviceMesh
+
 
 def test_device_mesh():
     physical_mesh_id = torch.arange(0, 16).reshape(2, 8)