Accept model type parameter in export_llama

Author: jackzhxng

examples/models/llama2/export_llama_lib.py

@@ -78,7 +78,7 @@
 
 
 EXECUTORCH_DEFINED_MODELS = ["llama2", "llama3", "llama3_1", "llama3_2"]
-TORCHTUNE_DEFINED_MODELS = []
+TORCHTUNE_DEFINED_MODELS = ["llama3_2_vision"]
 
 
 class WeightType(Enum):
@@ -798,11 +798,12 @@ def _load_llama_model(
         modelname = "llama2"
         model_class_name = "Llama2Model"
     elif modelname in TORCHTUNE_DEFINED_MODELS:
-        raise NotImplementedError("Torchtune Llama models are not yet supported in ExecuTorch export.")
+        if modelname == "llama3_2_vision":
+            model_class_name = "Llama3_2Decoder"
     else:
         raise ValueError(f"{modelname} is not a valid Llama model.")
 
-    model, example_inputs, example_kwarg_inputs, _ = (
+    model, example_inputs, example_kwarg_inputs, dynamic_shapes = (
         EagerModelFactory.create_model(
             modelname,
             model_class_name,