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

    /**
     * Get the value for the key 'index.field.important_content'. <br>
     * The value is, e.g. important_content <br>
     * comment: Field name for important content in the index.