[Model] Add SupportsMultiModal.get_language_model interface (#16007)

Signed-off-by: NickLucche <nlucches@redhat.com>

vllm/model_executor/models/idefics3.py

@@ -710,6 +710,9 @@ class Idefics3ForConditionalGeneration(nn.Module, SupportsMultiModal,
             e.flatten(0, 1) for e in image_features.split(num_patches.tolist())
         ]
 
+    def get_language_model(self) -> torch.nn.Module:
+        return self.model
+
     def get_multimodal_embeddings(
             self, **kwargs: object) -> Optional[MultiModalEmbeddings]:
         image_input = self._parse_and_validate_image_input(**kwargs)