feat(dataset-tools): add dataset utilities and example script

- Introduced dataset tools for LeRobotDataset, including functions for deleting episodes, splitting datasets, adding/removing features, and merging datasets.
- Added an example script demonstrating the usage of these utilities.
- Implemented comprehensive tests for all new functionalities to ensure reliability and correctness.

examples/use_dataset_tools.py

@@ -0,0 +1,111 @@
+#!/usr/bin/env python
+"""
+Example script demonstrating dataset tools utilities.
+
+This script shows how to:
+1. Delete episodes from a dataset
+2. Split a dataset into train/val sets
+3. Add/remove features
+4. Merge datasets
+
+Usage:
+    python examples/use_dataset_tools.py
+"""
+
+import numpy as np
+
+from lerobot.datasets.dataset_tools import (
+    add_feature,
+    delete_episodes,
+    merge_datasets,
+    remove_feature,
+    split_dataset,
+)
+from lerobot.datasets.lerobot_dataset import LeRobotDataset
+
+
+def main():
+    # Load an existing dataset (replace with your dataset)
+    dataset = LeRobotDataset("lerobot/pusht")
+
+    print(f"Original dataset: {dataset.meta.total_episodes} episodes, {dataset.meta.total_frames} frames")
+    print(f"Features: {list(dataset.meta.features.keys())}")
+
+    # Example 1: Delete episodes
+    print("\n1. Deleting episodes 0 and 2...")
+    filtered_dataset = delete_episodes(dataset, episode_indices=[0, 2], repo_id="pusht_filtered")
+    print(f"Filtered dataset: {filtered_dataset.meta.total_episodes} episodes")
+
+    # Example 2: Split dataset
+    print("\n2. Splitting dataset into train/val...")
+    splits = split_dataset(
+        dataset,
+        splits={"train": 0.8, "val": 0.2},
+    )
+    print(f"Train split: {splits['train'].meta.total_episodes} episodes")
+    print(f"Val split: {splits['val'].meta.total_episodes} episodes")
+
+    # Example 3: Add a feature
+    print("\n3. Adding a reward feature...")
+
+    # Method 1: Pre-computed values
+    reward_values = np.random.randn(dataset.meta.total_frames).astype(np.float32)
+    dataset_with_reward = add_feature(
+        dataset,
+        feature_name="reward",
+        feature_values=reward_values,
+        feature_info={
+            "dtype": "float32",
+            "shape": (1,),
+            "names": None,
+        },
+        repo_id="pusht_with_reward",
+    )
+
+    # Method 2: Using a callable
+    def compute_success(frame_dict, episode_idx, frame_idx):
+        # Example: mark last 10 frames of each episode as successful
+        episode_length = 10  # You'd get this from episode metadata
+        return float(frame_idx >= episode_length - 10)
+
+    dataset_with_success = add_feature(
+        dataset_with_reward,
+        feature_name="success",
+        feature_values=compute_success,
+        feature_info={
+            "dtype": "float32",
+            "shape": (1,),
+            "names": None,
+        },
+        repo_id="pusht_with_reward_and_success",
+    )
+
+    print(f"New features: {list(dataset_with_success.meta.features.keys())}")
+
+    # Example 4: Remove features
+    print("\n4. Removing the success feature...")
+    dataset_cleaned = remove_feature(dataset_with_success, feature_names="success", repo_id="pusht_cleaned")
+    print(f"Features after removal: {list(dataset_cleaned.meta.features.keys())}")
+
+    # Example 5: Merge datasets
+    print("\n5. Merging train and val splits back together...")
+    merged = merge_datasets([splits["train"], splits["val"]], output_repo_id="pusht_merged")
+    print(f"Merged dataset: {merged.meta.total_episodes} episodes")
+
+    # Example 6: Complex workflow
+    print("\n6. Complex workflow example...")
+
+    # Remove a camera if dataset has multiple
+    if len(dataset.meta.camera_keys) > 1:
+        camera_to_remove = dataset.meta.camera_keys[0]
+        print(f"Removing camera: {camera_to_remove}")
+        dataset_no_cam = remove_feature(
+            dataset, feature_names=camera_to_remove, repo_id="pusht_no_first_camera"
+        )
+        print(f"Remaining cameras: {dataset_no_cam.meta.camera_keys}")
+
+    print("\nDone! Check ~/.cache/huggingface/lerobot/ for the created datasets.")
+
+
+if __name__ == "__main__":
+    main()