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)
        self.redis.hset(
            key,
            mapping={
                str(idx): generation.text for idx, generation in enumerate(return_val)
            },
        )
[docs]    def clear(self, **kwargs: Any) -> None:
        """Clear cache. If `asynchronous` is True, flush asynchronously."""
        asynchronous = kwargs.get("asynchronous", False)
        self.redis.flushdb(asynchronous=asynchronous, **kwargs)
[docs]class RedisSemanticCache(BaseCache):
    """Cache that uses Redis as a vector-store backend."""
    # TODO - implement a TTL policy in Redis
[docs]    def __init__(
        self, redis_url: str, embedding: Embeddings, score_threshold: float = 0.2
    ):
        """Initialize by passing in the `init` GPTCache func
        Args:
            redis_url (str): URL to connect to Redis.
            embedding (Embedding): Embedding provider for semantic encoding and search.