text: Title: [Feature request] Please add from_single_file support in SanaTransformer2DModel to support first Sana Apache licensed model
  Body: **Is your feature request related to a problem? Please describe.**
  We all know Sana model is very good but unfortunately the LICENSE is restrictive.
  Recently a Sana finetuned model is released under Apache LICENSE. Unfortunately SanaTransformer2DModel does not support from_single_file to use it
  
  **Describe the solution you'd like.**
  
  ```python
  import torch
  from diffusers import SanaPipeline
  from diffusers import SanaTransformer2DModel
  model_path = "Efficient-Large-Model/Sana_1600M_1024px_MultiLing"
  dtype = torch.float16
  transformer = SanaTransformer2DModel.from_single_file (
  	"Swarmeta-AI/Twig-v0-alpha/Twig-v0-alpha-1.6B-2048x-fp16.pth",
  	torch_dtype=dtype,
  )
  pipe = SanaPipeline.from_pretrained(
  	pretrained_model_name_or_path=model_path,
  	transformer=transformer,
  	torch_dtype=dtype,
  	use_safetensors=True,
  )
  pipe.to("cuda")
  pipe.enable_model_cpu_offload()
  pipe.enable_vae_slicing()
  pipe.enable_vae_tiling()
  inference_params = {
  	"prompt": "rose flower",
  	"negative_prompt": "",
  	"height": 1024,
  	"width": 1024,
  	"guidance_scale": 4.0,
  	"num_inference_steps": 20,
  
  }
  image = pipe(**inference_params).images[0]
  image.save("sana.png")
  
  ```
  
  ```
  (venv) C:\aiOWN\diffuser_webui>python sana_apache.py
  Traceback (most recent call last):
    File "C:\aiOWN\diffuser_webui\sana_apache.py", line 6, in <module>
      transformer = SanaTransformer2DModel.from_single_file (
  AttributeError: type object 'SanaTransformer2DModel' has no attribute 'from_single_file'
  
  ```
  
  **Describe alternatives you've considered.**
  No alternatives available as far as I know
  
  **Additional context.**
  N.A.
  