[lora] factor out the overlaps in `save_lora_weights()`. (#12027)

* factor out the overlaps in save_lora_weights().

* remove comment.

* remove comment.

* up

* fix-copies

src/diffusers/loaders/lora_base.py

@@ -1064,6 +1064,41 @@ class LoraBaseMixin:
         save_function(state_dict, save_path)
         logger.info(f"Model weights saved in {save_path}")
 
+    @classmethod
+    def _save_lora_weights(
+        cls,
+        save_directory: Union[str, os.PathLike],
+        lora_layers: Dict[str, Dict[str, Union[torch.nn.Module, torch.Tensor]]],
+        lora_metadata: Dict[str, Optional[dict]],
+        is_main_process: bool = True,
+        weight_name: str = None,
+        save_function: Callable = None,
+        safe_serialization: bool = True,
+    ):
+        """
+        Helper method to pack and save LoRA weights and metadata. This method centralizes the saving logic for all
+        pipeline types.
+        """
+        state_dict = {}
+        final_lora_adapter_metadata = {}
+
+        for prefix, layers in lora_layers.items():
+            state_dict.update(cls.pack_weights(layers, prefix))
+
+        for prefix, metadata in lora_metadata.items():
+            if metadata:
+                final_lora_adapter_metadata.update(_pack_dict_with_prefix(metadata, prefix))
+
+        cls.write_lora_layers(
+            state_dict=state_dict,
+            save_directory=save_directory,
+            is_main_process=is_main_process,
+            weight_name=weight_name,
+            save_function=save_function,
+            safe_serialization=safe_serialization,
+            lora_adapter_metadata=final_lora_adapter_metadata if final_lora_adapter_metadata else None,
+        )
+
     @classmethod
     def _optionally_disable_offloading(cls, _pipeline):
         return _func_optionally_disable_offloading(_pipeline=_pipeline)