add_dynamic_partials example

        // Ensure that doing selective refresh on 404 template doesn't result in fallback rendering behavior (full refreshes).         status_header( 200 );

        $partials = json_decode( wp_unslash( $_POST['partials'] ), true );

        if ( ! is_array( $partials ) ) {
            wp_send_json_error( 'malformed_partials' );
        }

        $this->add_dynamic_partials( array_keys( $partials ) );

        /** * Fires immediately before partials are rendered. * * Plugins may do things like call wp_enqueue_scripts() and gather a list of the scripts * and styles which may get enqueued in the response. * * @since 4.5.0 * * @param WP_Customize_Selective_Refresh $refresh Selective refresh component. * @param array $partials Placements' context data for the partials rendered in the request. * The array is keyed by partial ID, with each item being an array of * the placements' context data. */