langchain/agents/structured_chat/base.py/StructuredChatAgent/_get_default_output_parser
class StructuredChatAgent:    def _get_default_output_parser(
        cls, llm: Optional[BaseLanguageModel] = None, **kwargs: Any
    ) -> AgentOutputParser:
        return StructuredChatOutputParserWithRetries.from_llm(llm=llm)