Do not load dataset information at instanciation

dan/datasets/download/images.py

@@ -46,7 +46,7 @@ class ImageDownloader:
 
     def __init__(
         self,
-        output: Path | None = None,
+        output: Path,
         max_width: int | None = None,
         max_height: int | None = None,
         image_extension: str = "",
@@ -57,9 +57,15 @@ class ImageDownloader:
         self.max_width = max_width
         self.max_height = max_height
         self.image_extension = image_extension
+        self.data: Dict = defaultdict(dict)
+        self.unknown_token = unknown_token
 
+    def load_split_data(self):
+        """
+        Load the dataset stored in `split.json` and initializes the charset.
+        """
         # Load split file
-        split_file = self.output / "split.json" if self.output else None
+        split_file = self.output / "split.json"
         self.split: Dict = (
             json.loads(split_file.read_text())
             if split_file and split_file.is_file()
@@ -68,9 +74,8 @@ class ImageDownloader:
 
         # Create directories
         for split_name in self.split:
-            (output / IMAGES_DIR / split_name).mkdir(parents=True, exist_ok=True)
+            (self.output / IMAGES_DIR / split_name).mkdir(parents=True, exist_ok=True)
 
-        self.data: Dict = defaultdict(dict)
         self.charset = set(
             chain.from_iterable(
                 split_data["text"] for split_data in self.split[TRAIN_NAME].values()
@@ -78,7 +83,6 @@ class ImageDownloader:
         )
 
         # Add unknown token to charset
-        self.unknown_token = unknown_token
         self.charset.add(self.unknown_token)
 
     def check_extraction(self, values: dict) -> str | None:
@@ -283,6 +287,7 @@ class ImageDownloader:
         a mapping of the images that have been correctly uploaded (identified by its path)
         to the ground-truth transcription (with NER tokens if needed).
         """
+        self.load_split_data()
         tasks: List[Dict[str, str]] = self.build_tasks()
         self.download_images(tasks)
         self.export()