langchain/client/models.py/ListRunsQueryParams/validate_time_range
class ListRunsQueryParams:    def validate_time_range(cls, values: Dict[str, Any]) -> Dict[str, Any]:
        """Validate that start_time <= end_time."""
        start_time = values.get("start_time")
        end_time = values.get("end_time")
        if start_time and end_time and start_time > end_time:
            raise ValueError("start_time must be <= end_time")
        return values