Fix signature for stop parameter

Author: abetlen

llama_cpp/llama.py

@@ -323,7 +323,7 @@ def _create_completion(
         top_p: float = 0.95,
         logprobs: Optional[int] = None,
         echo: bool = False,
-        stop: List[str] = [],
+        stop: Optional[List[str]] = [],
         repeat_penalty: float = 1.1,
         top_k: int = 40,
         stream: bool = False,
@@ -336,6 +336,7 @@ def _create_completion(
         prompt_tokens = self.tokenize(b" " + prompt.encode("utf-8"))
         text = b""
         returned_characters = 0
+        stop = stop if not None else []
 
         if self.verbose:
             llama_cpp.llama_reset_timings(self.ctx)
@@ -537,7 +538,7 @@ def create_completion(
         top_p: float = 0.95,
         logprobs: Optional[int] = None,
         echo: bool = False,
-        stop: List[str] = [],
+        stop: Optional[List[str]] = [],
         repeat_penalty: float = 1.1,
         top_k: int = 40,
         stream: bool = False,
@@ -592,7 +593,7 @@ def __call__(
         top_p: float = 0.95,
         logprobs: Optional[int] = None,
         echo: bool = False,
-        stop: List[str] = [],
+        stop: Optional[List[str]] = [],
         repeat_penalty: float = 1.1,
         top_k: int = 40,
         stream: bool = False,
@@ -698,7 +699,7 @@ def create_chat_completion(
         top_p: float = 0.95,
         top_k: int = 40,
         stream: bool = False,
-        stop: List[str] = [],
+        stop: Optional[List[str]] = [],
         max_tokens: int = 128,
         repeat_penalty: float = 1.1,
     ) -> Union[ChatCompletion, Iterator[ChatCompletionChunk]]:
@@ -717,6 +718,7 @@ def create_chat_completion(
         Returns:
             Generated chat completion or a stream of chat completion chunks.
         """
+        stop = stop if not None else []
         instructions = """Complete the following chat conversation between the user and the assistant. System messages should be strictly followed as additional instructions."""
         chat_history = "\n".join(
             f'{message["role"]} {message.get("user", "")}: {message["content"]}'