[checkpointio] fix async io (#6155)

Author: flybird11111

colossalai/checkpoint_io/general_checkpoint_io.py

@@ -8,8 +8,6 @@
 import torch.nn as nn
 from torch.optim import Optimizer
 
-from colossalai.utils.safetensors import move_and_save
-
 from .checkpoint_io_base import CheckpointIO
 from .index_file import CheckpointIndexFile
 from .utils import (
@@ -54,6 +52,7 @@ def save_unsharded_model(
             pass
 
         if use_async:
+            from colossalai.utils.safetensors import move_and_save
 
             if id(model) not in self.pinned_state_dicts:
                 self.pinned_state_dicts[id(model)] = create_pinned_state_dict(state_dict)

colossalai/checkpoint_io/utils.py

@@ -19,7 +19,6 @@
     to_global,
     to_global_for_customized_distributed_tensor,
 )
-from colossalai.utils.safetensors import move_and_save
 
 SAFE_WEIGHTS_NAME = "model.safetensors"
 WEIGHTS_NAME = "pytorch_model.bin"
@@ -289,6 +288,7 @@ def async_save_state_dict_shards(
     Returns:
         int: the total size of shards
     """
+    from colossalai.utils.safetensors import move_and_save
 
     total_size = 0
     shard_filenames = []