custom object serialization (#87)

lotus/cache.py

@@ -59,7 +59,7 @@ def serialize(value: Any) -> Any:
                     lotus.logger.warning(f"Unsupported type {type(value)} for serialization. Converting to string.")
                     return str(value)
 
-            serialize_self = serialize(self)
+            serialize_self = serialize(self._obj)
             serialized_kwargs = {key: serialize(value) for key, value in kwargs.items()}
             serialized_args = [serialize(arg) for arg in args]
             cache_key = hashlib.sha256(