refactor(datasets): replace untyped dict with typed DatasetInfo dataclass (#3472)

* refactor(datasets): replace untyped dict with typed DatasetInfo dataclass

Introduce typed DatasetInfo dataclass to replace untyped dict representation of info.json.

Changes:
- Add DatasetInfo dataclass with explicit fields and validation
- Implement __post_init__ for shape conversion (list ↔ tuple)
- Add dict-style compatibility layer (__getitem__, __setitem__, .get())
- Add from_dict() and to_dict() for JSON serialization
- Update io_utils to use load_info/write_info with DatasetInfo
- Update dataset utilities and metadata to use attribute access
- Remove aggregate.py dict-style field access
- Add tests fixture support for DatasetInfo

Benefits:
- Type safety with IDE auto-completion
- Validation at construction time
- Explicit schema documentation

* fix pre-commit

* update docstring inside DatasetInfo.from_dict()

* sorts the unknown to have deterministic output

Signed-off-by: Maxime Ellerbach <maxime@ellerbach.net>

* refactoring the last few old fieds


* fix crop dataset roi type mismatch


* use consistantly int for data and video_files_size_in_mb

---------

Signed-off-by: Maxime Ellerbach <maxime@ellerbach.net>
Co-authored-by: jjolla93 <jjolla93@gmail.com>

tests/datasets/test_aggregate.py

@@ -113,7 +113,7 @@ def assert_metadata_consistency(aggr_ds, ds_0, ds_1):
     """Test that metadata is correctly aggregated."""
     # Test basic info
     assert aggr_ds.fps == ds_0.fps == ds_1.fps, "FPS should be the same across all datasets"
-    assert aggr_ds.meta.info["robot_type"] == ds_0.meta.info["robot_type"] == ds_1.meta.info["robot_type"], (
+    assert aggr_ds.meta.info.robot_type == ds_0.meta.info.robot_type == ds_1.meta.info.robot_type, (
         "Robot type should be the same"
     )
 
@@ -153,8 +153,8 @@ def assert_video_frames_integrity(aggr_ds, ds_0, ds_1):
 
     video_keys = list(
         filter(
-            lambda key: aggr_ds.meta.info["features"][key]["dtype"] == "video",
-            aggr_ds.meta.info["features"].keys(),
+            lambda key: aggr_ds.meta.info.features[key]["dtype"] == "video",
+            aggr_ds.meta.info.features.keys(),
         )
     )
 

tests/datasets/test_dataset_metadata.py

@@ -161,7 +161,7 @@ def test_init_loads_existing_metadata(tmp_path, lerobot_dataset_metadata_factory
 
     assert meta.total_episodes == 3
     assert meta.total_frames == 150
-    assert meta.fps == info["fps"]
+    assert meta.fps == info.fps
 
 
 # ── Property accessors ───────────────────────────────────────────────

tests/datasets/test_lerobot_dataset.py

@@ -80,18 +80,18 @@ def _write_dataset_tree(
     )
     tasks = tasks_factory(total_tasks=1)
     episodes = episodes_factory(
-        features=info["features"],
-        fps=info["fps"],
+        features=info.features,
+        fps=info.fps,
         total_episodes=1,
         total_frames=3,
         tasks=tasks,
     )
-    stats = stats_factory(features=info["features"])
+    stats = stats_factory(features=info.features)
     hf_dataset = hf_dataset_factory(
-        features=info["features"],
+        features=info.features,
         tasks=tasks,
         episodes=episodes,
-        fps=info["fps"],
+        fps=info.fps,
     )
 
     create_info(root, info)