Count examples in lance

[lhoestq]

In [1]: from datasets import load_dataset_builder, StreamingDownloadManager

In [2]: b = load_dataset_builder("lance-format/openvid-lance")
Resolving data files: 100%|█| 240/240 [00:00<00:00, 42675.64it/s

In [3]: b.count_examples(StreamingDownloadManager())
Out[3]: {'train': 937957}

[HuggingFaceDocBuilderDev]

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