def start_evaluator(self) -> None:
        """Start the evaluator for the app."""
        # Validate.
        if not is_otel_tracing_enabled():
            raise ValueError(
                "This method is only supported for OTEL Tracing. Please enable OTEL tracing in the environment!"
            )
        if self._thread is not None:
            raise RuntimeError(
                "Evaluator thread already started. Please stop it before starting a new one."
            )
        # Create and start the evaluator thread.
        self._stop_event.clear()
        self._thread = threading.Thread(
            target=self._run_evaluator,
            daemon=True,
            name=f"evaluator_thread(app_name={self._app_name}, app_version={self._app_version})",
        )
        self._thread.start()
Start the evaluator for the app.
src/core/trulens/core/utils/evaluator.py