update docstr

Author: IrisRainbowNeko

src/diffusers/loaders/single_file_model.py

@@ -240,6 +240,11 @@ def from_single_file(cls, pretrained_model_link_or_path_or_dict: Optional[str] =
             revision (`str`, *optional*, defaults to `"main"`):
                 The specific model version to use. It can be a branch name, a tag name, a commit id, or any identifier
                 allowed by Git.
+            low_cpu_mem_usage (`bool`, *optional*, defaults to `True` if torch version >= 1.9.0 and
+                is_accelerate_available() else `False`): Speed up model loading only loading the pretrained weights
+                and not initializing the weights. This also tries to not use more than 1x model size in CPU memory
+                (including peak memory) while loading the model. Only supported for PyTorch >= 1.9.0. If you are using
+                an older version of PyTorch, setting this argument to `True` will raise an error.
             disable_mmap ('bool', *optional*, defaults to 'False'):
                 Whether to disable mmap when loading a Safetensors model. This option can perform better when the model
                 is on a network mount or hard drive, which may not handle the seeky-ness of mmap very well.