Add async support to semantic cache extension (#214)

This PR introduces new async compliant methods to the semantic cache
class using lazy index construction. Because the `AsyncSearchIndex`
requires an async redis python client, we needed to construct that class
lazily upon first usage within the semantic cache class. This PR fixes
some unclosed connection errors and is also in support of
BerriAI/litellm#5412 at LiteLLM.

redisvl/extensions/llmcache/base.py

@@ -31,7 +31,11 @@ def set_ttl(self, ttl: Optional[int] = None):
             self._ttl = None
 
     def clear(self) -> None:
-        """Clear the LLMCache of all keys in the index."""
+        """Clear the cache of all keys in the index."""
+        raise NotImplementedError
+
+    async def aclear(self) -> None:
+        """Async clear the cache of all keys in the index."""
         raise NotImplementedError
 
     def check(
@@ -41,6 +45,17 @@ def check(
         num_results: int = 1,
         return_fields: Optional[List[str]] = None,
     ) -> List[dict]:
+        """Check the cache based on a prompt or vector."""
+        raise NotImplementedError
+
+    async def acheck(
+        self,
+        prompt: Optional[str] = None,
+        vector: Optional[List[float]] = None,
+        num_results: int = 1,
+        return_fields: Optional[List[str]] = None,
+    ) -> List[dict]:
+        """Async check the cache based on a prompt or vector."""
         raise NotImplementedError
 
     def store(
@@ -50,7 +65,18 @@ def store(
         vector: Optional[List[float]] = None,
         metadata: Optional[dict] = {},
     ) -> str:
-        """Stores the specified key-value pair in the cache along with
+        """Store the specified key-value pair in the cache along with
+        metadata."""
+        raise NotImplementedError
+
+    async def astore(
+        self,
+        prompt: str,
+        response: str,
+        vector: Optional[List[float]] = None,
+        metadata: Optional[dict] = {},
+    ) -> str:
+        """Async store the specified key-value pair in the cache along with
         metadata."""
         raise NotImplementedError