[NFC] polish communication/p2p_v2.py code style (#2303)

colossalai/communication/p2p_v2.py

 #!/usr/bin/env python
 # -*- encoding: utf-8 -*-
 
-from typing import List, Tuple, Union, Any
-import pickle
 import io
+import pickle
+from typing import Any, List, Tuple, Union
 
 import torch
 import torch.distributed as dist
-from torch.distributed import distributed_c10d as c10d
 from torch.distributed import ProcessGroupNCCL
+from torch.distributed import distributed_c10d as c10d
 
 from colossalai.context.parallel_mode import ParallelMode
 from colossalai.core import global_context as gpc
@@ -23,7 +23,7 @@ def init_process_group():
 
     Args:
         None
-    
+
     Returns:
         None
     """
@@ -40,7 +40,7 @@ def _acquire_pair_group_handle(first_rank: int, second_rank: int) -> ProcessGrou
         second_rank (int): second rank in the pair
 
     Returns:
-        :class:`ProcessGroupNCCL`: the handle of the group consisting of the given two ranks 
+        :class:`ProcessGroupNCCL`: the handle of the group consisting of the given two ranks
     """
     if len(_pg_manager) == 0:
         init_process_group()
@@ -51,8 +51,8 @@ def _acquire_pair_group_handle(first_rank: int, second_rank: int) -> ProcessGrou
 
 
 def _cuda_safe_tensor_to_object(tensor: torch.Tensor, tensor_size: torch.Size) -> object:
-    """transform tensor to object with unpickle. 
-    Info of the device in bytes stream will be modified into current device before unpickling    
+    """transform tensor to object with unpickle.
+    Info of the device in bytes stream will be modified into current device before unpickling
 
     Args:
         tensor (:class:`torch.tensor`): tensor to be unpickled
@@ -78,9 +78,9 @@ def _cuda_safe_tensor_to_object(tensor: torch.Tensor, tensor_size: torch.Size) -
 def _broadcast_object_list(object_list: List[Any], src: int, dst: int, device=None):
     """This is a modified version of the broadcast_object_list in torch.distribution
     The only difference is that object will be move to correct device after unpickled.
-    If local_rank = src, then object list will be sent to rank src. Otherwise, object list will 
+    If local_rank = src, then object list will be sent to rank src. Otherwise, object list will
     be updated with data sent from rank src.
-    
+
     Args:
         object_list (List[Any]): list of object to broadcast
         src (int): source rank to broadcast
@@ -182,7 +182,7 @@ def _recv_object(src: int) -> Any:
 
     Args:
         src (int): source rank of data. local rank will receive data from src rank.
-    
+
     Returns:
         Any: Object received from src.
     """