Change path to posix (modeling_utils.py) (#6781)

* Change path to posix

* running isort

* run style and quality checks

---------
Co-authored-by: Sayak Paul <spsayakpaul@gmail.com>

src/diffusers/models/modeling_utils.py

@@ -20,6 +20,7 @@ import os
 import re
 from collections import OrderedDict
 from functools import partial
+from pathlib import Path
 from typing import Any, Callable, List, Optional, Tuple, Union
 
 import safetensors
@@ -367,18 +368,18 @@ class ModelMixin(torch.nn.Module, PushToHubMixin):
         # Save the model
         if safe_serialization:
             safetensors.torch.save_file(
-                state_dict, os.path.join(save_directory, weights_name), metadata={"format": "pt"}
+                state_dict, Path(save_directory, weights_name).as_posix(), metadata={"format": "pt"}
             )
         else:
-            torch.save(state_dict, os.path.join(save_directory, weights_name))
+            torch.save(state_dict, Path(save_directory, weights_name).as_posix())
 
-        logger.info(f"Model weights saved in {os.path.join(save_directory, weights_name)}")
+        logger.info(f"Model weights saved in {Path(save_directory, weights_name).as_posix()}")
 
         if push_to_hub:
             # Create a new empty model card and eventually tag it
             model_card = load_or_create_model_card(repo_id, token=token)
             model_card = populate_model_card(model_card)
-            model_card.save(os.path.join(save_directory, "README.md"))
+            model_card.save(Path(save_directory, "README.md").as_posix())
 
             self._upload_folder(
                 save_directory,