Array
(
    [metadata.author] => Array
        (
            [buckets] => Array
                (
                    [0] => Array
                        (
                            [key] => Me
                            [doc_count] => 1
                        )

                    [1] => Array
                        (
                            [key] => Av
                            [doc_count] => 1
                        )

                )

        )

    [metadata.series] => Array
        (
            [buckets] => Array
                (
                    [0] => Array
                        (
                            [key] => 
                            [doc_count] => 1
                        )

                )

        )

    [metadata.publisher] => Array
        (
            [buckets] => Array
                (
                    [0] => Array
                        (
                            [key] => BoD - Books on Demand
                            [doc_count] => 1
                        )

                )

        )

    [metadata.release_year] => Array
        (
            [buckets] => Array
                (
                    [0] => Array
                        (
                            [key] => 2020
                            [doc_count] => 1
                        )

                )

        )

    [metadata.cover_type] => Array
        (
            [buckets] => Array
                (
                    [0] => Array
                        (
                            [key] => 2
                            [doc_count] => 1
                        )

                )

        )

    [stock_lt_status] => Array
        (
            [buckets] => Array
                (
                    [0] => Array
                        (
                            [key] => 0
                            [doc_count] => 1
                        )

                )

        )

)