Fix special tokens mask in encode

transformers/tokenization_utils.py

@@ -973,7 +973,7 @@ class PreTrainedTokenizer(object):
             token_type_ids = [0] * len(ids) + ([1] * len(pair_ids) if pair else [])
 
         if return_special_tokens_mask:
-            encoded_inputs["special_tokens_mask"] = special_tokens_mask
+            encoded_inputs["special_tokens_mask"] = self.get_special_tokens_mask(ids, pair_ids)
 
         encoded_inputs["input_ids"] = sequence
         if return_token_type_ids: