[Model] Add UltravoxModel and UltravoxConfig (#7615)

tests/models/test_bart.py

@@ -12,6 +12,7 @@ if not is_cpu():
     # (xFormers, etc.)
 
     import pytest
+    from transformers import AutoModelForSeq2SeqLM
 
     from vllm.sequence import SampleLogprobs
 
@@ -131,7 +132,7 @@ if not is_cpu():
         }
 
         with hf_runner(model, dtype=dtype,
-                       is_encoder_decoder_model=True) as hf_model:
+                       auto_cls=AutoModelForSeq2SeqLM) as hf_model:
             hf_outputs = (
                 hf_model.generate_encoder_decoder_greedy_logprobs_limit(
                     test_case_prompts,