Array
(
    [metadata.author] => Array
        (
            [buckets] => Array
                (
                )

        )

    [metadata.series] => Array
        (
            [buckets] => Array
                (
                )

        )

    [metadata.publisher] => Array
        (
            [buckets] => Array
                (
                )

        )

    [metadata.release_year] => Array
        (
            [buckets] => Array
                (
                )

        )

    [metadata.cover_type] => Array
        (
            [buckets] => Array
                (
                )

        )

    [stock_lt_status] => Array
        (
            [buckets] => Array
                (
                )

        )

)