* The value is, e.g. _version <br>
     * comment: Field name for version in the index.
     * @return The value of found property. (NotNull: if not found, exception but basically no way)
     */
    String getIndexFieldVersion();

    /**
     * Get the value for the key 'index.field.seq_no'. <br>
     * The value is, e.g. _seq_no <br>
     * comment: Field name for sequence number in the index.