Use max_length in AutoSeq2SeqLM (#551)

lm_eval/models/huggingface.py

@@ -351,7 +351,7 @@ class HuggingFaceAutoLM(BaseLM):
         """Return the maximum sequence length of the model.
         NOTE: Different model configurations have different max sequence length
         attribute names.
-            - n_positions: (CTRLConfig)
+            - n_positions: (CTRLConfig, T5Config)
             - max_position_embeddings: (BartConfig, RoFormerConfig)
             - n_ctx: (GPT2Config)
         NOTE: For relative position encoded models you should specify the max
@@ -543,15 +543,6 @@ class AutoSeq2SeqLM(HuggingFaceAutoLM):
     AUTO_MODEL_CLASS = transformers.AutoModelForSeq2SeqLM
     AUTO_PEFT_CLASS = peft.PeftModel
 
-    @property
-    def max_length(self) -> int:
-        """Return the maximum sequence length of the model.
-        TODO: Currently only works for relative position encoded Seq2Seq models.
-        """
-        if self._max_length is not None:
-            return self._max_length
-        return self._DEFAULT_MAX_LENGTH
-
     def loglikelihood(
         self, requests: List[Tuple[str, str]]
     ) -> List[Tuple[float, bool]]: