"Please install it with `pip install redis`."
            )
        if not isinstance(redis_, Redis):
            raise ValueError("Please pass in Redis object.")
        self.redis = redis_
        self.ttl = ttl
    def _key(self, prompt: str, llm_string: str) -> str:
        """Compute key from prompt and llm_string"""
        return _hash(prompt + llm_string)
[docs]    def lookup(self, prompt: str, llm_string: str) -> Optional[RETURN_VAL_TYPE]:
        """Look up based on prompt and llm_string."""
        generations = []
        # Read from a Redis HASH
        results = self.redis.hgetall(self._key(prompt, llm_string))
        if results:
            for _, text in results.items():
                generations.append(Generation(text=text))
        return generations if generations else None
[docs]    def update(self, prompt: str, llm_string: str, return_val: RETURN_VAL_TYPE) -> None:
        """Update cache based on prompt and llm_string."""
        for gen in return_val:
            if not isinstance(gen, Generation):
                raise ValueError(
                    "RedisCache only supports caching of normal LLM generations, "
                    f"got {type(gen)}"
                )
            if isinstance(gen, ChatGeneration):
                warnings.warn(
                    "NOTE: Generation has not been cached. RedisCache does not"
                    " support caching ChatModel outputs."
                )
                return
        # Write to a Redis HASH
        key = self._key(prompt, llm_string)
        with self.redis.pipeline() as pipe:
            pipe.hset(
                key,
                mapping={
                    str(idx): generation.text
                    for idx, generation in enumerate(return_val)
                },
            )