fix: yield from super loader

src/tablegpt/retriever/loader.py

@@ -66,7 +66,8 @@ def lazy_load(self) -> Iterator[Document]:
     async def alazy_load(self) -> AsyncIterator[Document]:
         """A lazy loader for Documents."""
         # TODO: pandas does not support async read_csv yet. We might need to async read the file first.
-        return await super().alazy_load()
+        async for doc in super().alazy_load():
+            yield doc
 
     def column2docs(self, column: Series) -> Iterator[Document]:
         # If a string column contains NaN, it will be presented as object dtype.