langchain/callbacks/whylabs_callback.py/WhyLabsCallbackHandler/on_llm_start
class WhyLabsCallbackHandler:    def on_llm_start(
        self, serialized: Dict[str, Any], prompts: List[str], **kwargs: Any
    ) -> None:
        """Pass the input prompts to the logger"""
        for prompt in prompts:
            self.logger.log({"prompt": prompt})