langchain/cache.py/SQLAlchemyCache/lookup
class SQLAlchemyCache:    def lookup(self, prompt: str, llm_string: str) -> Optional[RETURN_VAL_TYPE]:
        """Look up based on prompt and llm_string."""
        stmt = (
            select(self.cache_schema.response)
            .where(self.cache_schema.prompt == prompt)  # type: ignore
            .where(self.cache_schema.llm == llm_string)
            .order_by(self.cache_schema.idx)
        )
        with Session(self.engine) as session:
            rows = session.execute(stmt).fetchall()
            if rows:
                return [Generation(text=row[0]) for row in rows]
        return None