try fix 7

src/lerobot/datasets/lerobot_dataset.py

@@ -1043,17 +1043,28 @@ class LeRobotDataset(torch.utils.data.Dataset):
     def __getitem__(self, idx) -> dict:
         # Ensure dataset is loaded when we actually need to read from it
         self._ensure_hf_dataset_loaded()
+
+        # Get the single, current-timestep item
         item = self.hf_dataset[idx]
         ep_idx = item["episode_index"].item()
 
         query_indices = None
         if self.delta_indices is not None:
+            # 1. Get indices for all deltas
             query_indices, padding = self._get_query_indices(idx, ep_idx)
+
+            # 2. Query non-image, non-video features
             query_result = self._query_hf_dataset(query_indices)
             item = {**item, **padding}
             for key, val in query_result.items():
                 item[key] = val
 
+            # 3. Query image features (which are not in _query_hf_dataset)
+            for key in self.meta.image_keys:
+                if key in query_indices:
+                    # hf_dataset[query_indices[key]][key] returns a LIST of PIL.Image objects
+                    item[key] = torch.stack(self.hf_dataset[query_indices[key]][key])
+
         if len(self.meta.video_keys) > 0:
             current_ts = item["timestamp"].item()
             query_timestamps = self._get_query_timestamps(current_ts, query_indices)