/** The key of the configuration. e.g. _seq_no */
    String INDEX_FIELD_seq_no = "index.field.seq_no";

    /** The key of the configuration. e.g. _primary_term */
    String INDEX_FIELD_primary_term = "index.field.primary_term";

    /** The key of the configuration. e.g. lang */
    String INDEX_FIELD_LANG = "index.field.lang";

    /** The key of the configuration. e.g. has_cache */