Fix max length in run_plm script (#8738)

examples/language-modeling/run_plm.py

@@ -93,11 +93,11 @@ class DataTrainingArguments:
     overwrite_cache: bool = field(
         default=False, metadata={"help": "Overwrite the cached training and evaluation sets"}
     )
-    max_seq_length: Optional[int] = field(
-        default=None,
+    max_seq_length: int = field(
+        default=512,
         metadata={
             "help": "The maximum total input sequence length after tokenization. Sequences longer "
-            "than this will be truncated. Default to the max input length of the model."
+            "than this will be truncated."
         },
     )
     preprocessing_num_workers: Optional[int] = field(
@@ -286,9 +286,6 @@ def main():
             load_from_cache_file=not data_args.overwrite_cache,
         )
 
-        if data_args.max_seq_length is None:
-            max_seq_length = tokenizer.model_max_length
-        else:
         if data_args.max_seq_length > tokenizer.model_max_length:
             logger.warn(
                 f"The max_seq_length passed ({data_args.max_seq_length}) is larger than the maximum length for the"