Reset cache ttl when no arg is passed (#181)

This PR resets the cache entry TTL to infinite/no expiration if we call
`set_ttl()` with no arguments. Otherwise once a TTL is set, it can only
be changed to another integer.

Author: justin-cechmanek

redisvl/extensions/llmcache/base.py

@@ -28,6 +28,8 @@ def set_ttl(self, ttl: Optional[int] = None):
             if not isinstance(ttl, int):
                 raise ValueError(f"TTL must be an integer value, got {ttl}")
             self._ttl = int(ttl)
+        else:
+            self._ttl = None
 
     def clear(self) -> None:
         """Clear the LLMCache of all keys in the index."""

tests/integration/test_llmcache.py

@@ -70,6 +70,12 @@ def test_set_ttl(cache):
     assert cache.ttl == 5
 
 
+def test_reset_ttl(cache):
+    cache.set_ttl(4)
+    cache.set_ttl()
+    assert cache.ttl is None
+
+
 # Test basic store and check functionality
 def test_store_and_check(cache, vectorizer):
     prompt = "This is a test prompt."