langchain/callbacks/tracers/langchain.py/LangChainTracer/__init__
class LangChainTracer:    def __init__(
        self,
        tenant_id: Optional[str] = None,
        example_id: Optional[UUID] = None,
        session_name: Optional[str] = None,
        session_extra: Optional[Dict[str, Any]] = None,
        **kwargs: Any,
    ) -> None:
        """Initialize the LangChain tracer."""
        super().__init__(**kwargs)
        self.session: Optional[TracerSession] = None
        self._endpoint = get_endpoint()
        self._headers = get_headers()
        self.tenant_id = tenant_id
        self.example_id = example_id
        self.session_name = session_name or os.getenv("LANGCHAIN_SESSION", "default")
        self.session_extra = session_extra