[Bugfix] Fix LM detection for Nemotron Parse (#42641)

Signed-off-by: DarkLight1337 <tlleungac@connect.ust.hk>

vllm/model_executor/models/interfaces.py

@@ -207,7 +207,8 @@ class SupportsMultiModal(Protocol):
 
         raise NotImplementedError(
             f"No language model found in {type(self).__name__}! "
-            "You should initialize it via `_mark_language_model`."
+            "You should initialize it via `_mark_language_model`, "
+            "and make sure `embed_input_ids` is implemented."
         )
 
     @contextmanager

vllm/model_executor/models/nemotron_parse.py

@@ -281,6 +281,9 @@ class MBartDecoderNoPos(nn.Module):
         self.layernorm_embedding = nn.LayerNorm(config.d_model)
         self.layer_norm = nn.LayerNorm(config.d_model)
 
+    def embed_input_ids(self, input_ids: torch.Tensor) -> torch.Tensor:
+        return self.embed_tokens(input_ids)
+
     def forward(
         self,
         decoder_input_ids: torch.Tensor | None,