[Core] Registry for processing model inputs (#5214)

Co-authored-by: ywang96 <ywang@roblox.com>

examples/phi3v_example.py

@@ -11,7 +11,7 @@ def run_phi3v():
     model_path = "microsoft/Phi-3-vision-128k-instruct"
 
     # Note: The model has 128k context length by default which may cause OOM
-    # If that's the case, override `max_model_len` with a smaller value via args
+    # In this example, we override max_model_len to 2048.
     llm = LLM(
         model=model_path,
         trust_remote_code=True,
@@ -19,6 +19,7 @@ def run_phi3v():
         image_token_id=32044,
         image_input_shape="1,3,1008,1344",
         image_feature_size=1921,
+        max_model_len=2048,
     )
 
     image = Image.open("images/cherry_blossom.jpg")