[Bugfix]: Fix TokenizerLike interface

vllm/tokenizers/mistral.py

@@ -309,6 +309,9 @@ def _get_special_tokens(self, all_special_ids: list[int]) -> list[str]:
             for i in all_special_ids
         ]
 
+    def num_special_tokens_to_add(self) -> int:
+        return len(self.encode(""))
+
     # the following attributes are set to fit vLLM's design and are used
     # by the structured output backends.
     @property