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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def dataset(ctx, client, revision, datadir, format):
 """Handle datasets."""

    ctx.meta['renku.datasets.datadir'] = datadir

    if ctx.invoked_subcommand is not None:
        return

    if revision is None:
        datasets = client.datasets.values()
    else:
        datasets = client.datasets_from_commit(client.repo.commit(revision))

    DATASETS_FORMATS[format](client, datasets)