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

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

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