langchain/evaluation/agents/trajectory_eval_chain.py/TrajectoryEvalChain/from_llm
class TrajectoryEvalChain:    def from_llm(
        cls,
        llm: ChatOpenAI,
        agent_tools: Sequence[BaseTool],
        output_parser: Optional[TrajectoryOutputParser] = None,
        return_reasoning: bool = False,
    ) -> "TrajectoryEvalChain":
        eval_chain = LLMChain(llm=llm, prompt=EVAL_CHAT_PROMPT)
        return cls(
            agent_tools=agent_tools,
            return_reasoning=return_reasoning,
            eval_chain=eval_chain,
            output_parser=output_parser or TrajectoryOutputParser(),
        )