community[minor]: Add async methods to CassandraLoader (#20609)

Co-authored-by: Eugene Yurtsev <eyurtsev@gmail.com>

libs/community/langchain_community/utilities/cassandra.py

@@ -0,0 +1,24 @@
+from __future__ import annotations
+
+import asyncio
+from typing import TYPE_CHECKING, Any, Callable
+
+if TYPE_CHECKING:
+    from cassandra.cluster import ResponseFuture
+
+
+async def wrapped_response_future(
+    func: Callable[..., ResponseFuture], *args: Any, **kwargs: Any
+) -> Any:
+    loop = asyncio.get_event_loop()
+    asyncio_future = loop.create_future()
+    response_future = func(*args, **kwargs)
+
+    def success_handler(_: Any) -> None:
+        loop.call_soon_threadsafe(asyncio_future.set_result, response_future.result())
+
+    def error_handler(exc: BaseException) -> None:
+        loop.call_soon_threadsafe(asyncio_future.set_exception, exc)
+
+    response_future.add_callbacks(success_handler, error_handler)
+    return await asyncio_future