updated product_exists to match new scheme

preprocessor/transfer/s3.py

 import os
 from functools import cached_property
-from typing import TYPE_CHECKING, Union, Dict, List
+from typing import TYPE_CHECKING, Union, Dict, List, Tuple
 
 import boto3
 import botocore
@@ -92,9 +92,11 @@ class S3Uploader(Base, Uploader):
 
         return local_remote_mapping
 
-    def product_exists(self, remote_dir: str) -> bool:
+    def product_exists(
+        self, remote_dir: str, expected_files_count: int = 2
+    ) -> Tuple[bool, List[str]]:
         objects = self.client.list_objects_v2(Bucket=self.bucket, Prefix=remote_dir)
-        if len(objects["Contents"]) >= 2:
-            return True
+        if len(objects["Contents"]) >= expected_files_count:
+            return True, [obj["Key"] for obj in objects["Contents"]]
 
-        return False
+        return False, []