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

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

vllm/model_executor/models/glm4v.py

@@ -596,6 +596,9 @@ class GLM4VForCausalLM(ChatGLMBaseModel, SupportsLoRA, SupportsPP,
 
         return self.transformer.vision(pixel_values)
 
+    def get_language_model(self) -> torch.nn.Module:
+        return self.transformer
+
     def get_multimodal_embeddings(
             self, **kwargs: object) -> Optional[MultiModalEmbeddings]:
         image_input = self._parse_and_validate_image_input(**kwargs)