Filter CPT by Custom Taxonomy in WP Dashboard

functions.php

<?php // <~ don't add me in

add_action( 'restrict_manage_posts', 'filter_backend_by_taxonomies' , 99, 2);
/* Filter CPT via Custom Taxonomy */
/* https://generatewp.com/filtering-posts-by-taxonomies-in-the-dashboard/ */

function filter_backend_by_taxonomies( $post_type, $which ) {

// Apply this to a specific CPT
if ( 'light' !== $post_type )
    return;

// A list of custom taxonomy slugs to filter by
$taxonomies = array( 'light_category' );

foreach ( $taxonomies as $taxonomy_slug ) {

    // Retrieve taxonomy data
    $taxonomy_obj = get_taxonomy( $taxonomy_slug );
    $taxonomy_name = $taxonomy_obj->labels->name;

    // Retrieve taxonomy terms
    $terms = get_terms( $taxonomy_slug );

    // Display filter HTML
    echo "<select name='{$taxonomy_slug}' id='{$taxonomy_slug}' class='postform'>";
    echo '<option value="">' . sprintf( esc_html__( 'Show All %s', 'text_domain' ), $taxonomy_name ) . '</option>';
    foreach ( $terms as $term ) {
        printf(
            '<option value="%1$s" %2$s>%3$s (%4$s)</option>',
            $term->slug,
            ( ( isset( $_GET[$taxonomy_slug] ) && ( $_GET[$taxonomy_slug] == $term->slug ) ) ? ' selected="selected"' : '' ),
            $term->name,
            $term->count
        );
    }
    echo '</select>';
}

}