init req

omagent_core/models/llms/openai_gpt.py

@@ -58,7 +58,7 @@ class OpenaiGPTLLM(BaseLLM):
         description="The top logprobs of LLM, logprobs must be set to true if this parameter is used",
     )
     stop: Union[str, List[str], None] = Field(
-        default=None,
+        default='',
         description="Specifies stop sequences that will halt text generation, can be string or list of strings",
     )
     stream_options: Optional[dict] = Field(