Fatal error: Uncaught Error: Call to undefined function add_filter() in /home/anirqfxq/public_html/wp-content/plugins/gutenberg/lib/experimental/class-gutenberg-hierarchical-sort.php:159 Stack trace: #0 {main} thrown in /home/anirqfxq/public_html/wp-content/plugins/gutenberg/lib/experimental/class-gutenberg-hierarchical-sort.php on line 159