add note about serialization (huggingface#6764)

Author: sayakpaul

docs/source/en/tutorials/using_peft_for_inference.md

@@ -206,3 +206,13 @@ pipe.fuse_lora(adapter_names=["pixel", "toy"])
 prompt = "toy_face of a hacker with a hoodie, pixel art"
 image = pipe(prompt, num_inference_steps=30, generator=torch.manual_seed(0)).images[0]
 ```
+
+## Saving a pipeline after fusing the adapters
+
+To properly save a pipeline after it's been loaded with the adapters, it should be serialized like so:
+
+```python
+pipe.fuse_lora(lora_scale=1.0)
+pipe.unload_lora_weights()
+pipe.save_pretrained("path-to-pipeline")
+```