Fixing typing

harvester/harvester.py

 import json
 import logging
-from typing import Iterator, Optional, Union
+from typing import Iterator, Optional
 
 from redis import Redis
 
@@ -18,7 +18,7 @@ def stringify(
     result: Iterator[dict],
     mode: str = "item",
     extract_property: Optional[str] = None,
-) -> Iterator[Union[dict, str]]:
+) -> Iterator[str]:
     if mode == "item":
         yield from (json.dumps(item, default=str) for item in result)
     elif mode == "property":