protected function __construct() {

    /* Add filters which get applied to the get_options() results. */
    $this->add_default_filters(); // Return defaults if option not set.
    $this->add_option_filters(); // Merge with defaults if option *is* set.


    if ( $this->multisite_only !== true ) {
      
/**
 * The option validation routines remove the default filters to prevent failing
 * to insert an option if it's new. Let's add them back afterwards.
 */
      add_action( 'add_option', [ $this, 'add_default_filters' ] ); // Adding back after INSERT.

      add_action( 'update_option', [ $this, 'add_default_filters' ] );

      // Refills the cache when the option has been updated.
      add_action( 'update_option_' . $this->option_name, [ 'WPSEO_Options', 'clear_cache' ], 10 );
    }
    elseif ( is_multisite() ) {
      /*
			 * The option validation routines remove the default filters to prevent failing
			 * to insert an option if it's new. Let's add them back afterwards.
			 *
			 * For site_options, this method is not foolproof as these actions are not fired
			 * on an insert/update failure. Please use the WPSEO_Options::update_site_option() method
			 * for updating site options to make sure the filters are in place.
			 */
      add_action( 'add_site_option_' . $this->option_name, [ $this, 'add_default_filters' ] );
      add_action( 'update_site_option_' . $this->option_name, [ $this, 'add_default_filters' ] );

      // Refills the cache when the option has been updated.
      add_action( 'update_site_option_' . $this->option_name, [ 'WPSEO_Options', 'clear_cache' ], 1, 0 );
    }


    /*
		 * Make sure the option will always get validated, independently of register_setting()
		 * (only available on back-end).
		 */
    add_filter( 'sanitize_option_' . $this->option_name, [ $this, 'validate' ] );

    // Flushes the rewrite rules when option is updated.
    add_action( 'update_option_' . $this->option_name, [ 'WPSEO_Utils', 'clear_rewrites' ] );

    /* Register our option for the admin pages */
    add_action( 'admin_init', [ $this, 'register_setting' ] )  <;


    /* Set option group name if not given */
    if ( ! isset( $this->group_name ) || $this->group_name === '' ) {
      $this->group_name = 'yoast_' . $this->option_name . '_options';
    }

    /* Translate some defaults as early as possible - textdomain is loaded in init on priority 1. */
    if ( method_exists( $this, 'translate_defaults' ) ) {
      add_action( 'init', [ $this, 'translate_defaults' ], 2 );
    }

    
/**
 * Enrich defaults once custom post types and taxonomies have been registered
 * which is normally done on the init action.
 *
 * @todo [JRF/testers] Verify that none of the options which are only available after
 * enrichment are used before the enriching.
 */
    if ( method_exists( $this, 'enrich_defaults' ) ) {
      add_action( 'init', [ $this, 'enrich_defaults' ], 99 );
    }
  }