async def async_delete_messages(self, key: str) -> Optional[List[ChatMessage]]:
        """
        Delete messages for a key.

        Args:
            key (str): The key to delete messages from.

        Returns:
            Optional[List[ChatMessage]]: Always returns None in this implementation.

        """
        await self._async_redis_client.delete(key)
        return None

        Delete messages for a key.

        Args:
            key (str): The key to delete messages from.

        Returns:
            Optional[List[ChatMessage]]: Always returns None in this implementation.

        
llama-index-integrations/storage/chat_store/llama-index-storage-chat-store-upstash/llama_index/storage/chat_store/upstash/base.py