Add relative_download_dir to Resource class.

PiperOrigin-RevId: 680463547

Author: fineguy

tensorflow_datasets/core/download/download_manager.py

@@ -318,8 +318,10 @@ def downloaded_size(self) -> int:
   def _get_dl_path(
       self, resource: resource_lib.Resource, checksum: str | None = None
   ) -> epath.Path:
-    return self._download_dir / resource_lib.get_dl_fname(
-        resource.url, checksum
+    return (
+        self._download_dir
+        / resource.relative_download_dir
+        / resource_lib.get_dl_fname(resource.url, checksum)
     )
 
   @property

tensorflow_datasets/core/download/resource.py

@@ -285,6 +285,7 @@ def __init__(
       url: str | None = None,
       extract_method: ExtractMethod | None = None,
       path: epath.PathLike | None = None,
+      relative_download_dir: epath.PathLike = '',
   ):
     """Resource constructor.
 
@@ -294,10 +295,13 @@ def __init__(
         set, will be guessed from downloaded file name `original_fname`.
       path: Path of resource on local disk. Can be None if resource has not be
         downloaded yet. In such case, `url` must be set.
+      relative_download_dir: Optional directory for downloading relative to
+        `download_dir`.
     """
     self.url = url
     self._extract_method = extract_method
     self.path: epath.Path = epath.Path(path) if path else None  # pytype: disable=annotation-type-mismatch  # attribute-variable-annotations
+    self.relative_download_dir = relative_download_dir
 
   @classmethod
   def exists_locally(cls, path: epath.Path) -> bool: