[Type hint] Score SDE VE pipeline (#325)

src/diffusers/pipelines/score_sde_ve/pipeline_score_sde_ve.py

 #!/usr/bin/env python3
 import warnings
+from typing import Optional
 
 import torch
 
 from diffusers import DiffusionPipeline
 
+from ...models import UNet2DModel
+from ...schedulers import ScoreSdeVeScheduler
+
 
 class ScoreSdeVePipeline(DiffusionPipeline):
-    def __init__(self, unet, scheduler):
+
+    unet: UNet2DModel
+    scheduler: ScoreSdeVeScheduler
+
+    def __init__(self, unet: UNet2DModel, scheduler: DiffusionPipeline):
         super().__init__()
         self.register_modules(unet=unet, scheduler=scheduler)
 
     @torch.no_grad()
-    def __call__(self, batch_size=1, num_inference_steps=2000, generator=None, output_type="pil", **kwargs):
+    def __call__(
+        self,
+        batch_size: int = 1,
+        num_inference_steps: int = 2000,
+        generator: Optional[torch.Generator] = None,
+        output_type: Optional[str] = "pil",
+        **kwargs,
+    ):
         if "torch_device" in kwargs:
             device = kwargs.pop("torch_device")
             warnings.warn(