fix(robomme): align docs and tests with nested pixels obs layout

Addresses PR #3311 review feedback:
- Docs: correct observation keys to `pixels/image` / `pixels/wrist_image`
  (mapped to `observation.images.image` / `observation.images.wrist_image`)
  and drop the now-obsolete column-rename snippet.
- Tests: assert `result["pixels"]["image"]` instead of flat `pixels/image`,
  matching the nested layout required by `preprocess_observation()`.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

docs/source/robomme.mdx

@@ -109,15 +109,9 @@ dataset = LeRobotDataset("lerobot/robomme")
 
 ### Feature key alignment (training)
 
-The env wrapper exposes `front_rgb` and `wrist_rgb` as observation keys. The `features_map` in `RoboMMEEnv` maps these to `obs_images.front` and `obs_images.wrist` for the policy.
+The env wrapper exposes `pixels/image` and `pixels/wrist_image` as observation keys. The `features_map` in `RoboMMEEnv` maps these to `observation.images.image` and `observation.images.wrist_image` for the policy. State is exposed as `agent_pos` and maps to `observation.state`.
 
-The dataset uses `image` and `wrist_image` as column names. When fine-tuning from the dataset, you may need to rename columns to match your policy's expected input keys:
+The dataset's `image` and `wrist_image` columns already align with the policy input keys, so no renaming is needed when fine-tuning.
-
-```python
-dataset = LeRobotDataset("lerobot/robomme")
-# rename dataset columns if needed:
-# dataset.hf_dataset = dataset.hf_dataset.rename_column("image", "front_rgb")
-```
 
 ## Action Spaces
 

tests/test_robomme_env.py

@@ -118,7 +118,11 @@ def test_robomme_features_action_dim_ee_pose():
 
 def test_convert_obs_list_format():
     """_convert_obs takes the last element from list-format obs fields and
-    emits the lerobot-canonical keys (pixels/image, pixels/wrist_image, agent_pos)."""
+    emits a nested ``pixels`` dict (image, wrist_image) plus ``agent_pos``.
+
+    The nested layout is required so ``preprocess_observation()`` in
+    ``envs/utils.py`` maps each camera to ``observation.images.<cam>``.
+    """
     _install_robomme_stub()
     try:
         from lerobot.envs.robomme import RoboMMEGymEnv
@@ -138,8 +142,8 @@ def test_convert_obs_list_format():
         }
 
         result = env._convert_obs(obs_raw)
-        np.testing.assert_array_equal(result["pixels/image"], front)
+        np.testing.assert_array_equal(result["pixels"]["image"], front)
-        np.testing.assert_array_equal(result["pixels/wrist_image"], wrist)
+        np.testing.assert_array_equal(result["pixels"]["wrist_image"], wrist)
         assert result["agent_pos"].shape == (8,)
         np.testing.assert_array_almost_equal(result["agent_pos"][:7], joints)
         assert result["agent_pos"][7] == gripper[0]
@@ -163,8 +167,8 @@ def test_convert_obs_array_format():
             "gripper_state_list": np.zeros(2, dtype=np.float32),
         }
         result = env._convert_obs(obs_raw)
-        assert result["pixels/image"].shape == (256, 256, 3)
+        assert result["pixels"]["image"].shape == (256, 256, 3)
-        assert result["pixels/wrist_image"].shape == (256, 256, 3)
+        assert result["pixels"]["wrist_image"].shape == (256, 256, 3)
         assert result["agent_pos"].shape == (8,)
     finally:
         _uninstall_robomme_stub()